Well the first thing I tried to do with .8 is take a look at the changes in the power bi files so I grabbed PowerBI-storage.zip and tried opening each file. I get this with every file and no option to get past to the prompt where I can see the transformed data.

Tried on three different systems just to be sure.

Feedback Type:
Frown (Error)

Error Message:
Error converting value {null} to type 'System.Boolean'. Path 'ReportSettings.UserConsentsToCompositeModels', line 1, position 55.

Stack Trace:
Newtonsoft.Json.JsonSerializationException
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.EnsureType(JsonReader reader, Object value, CultureInfo culture, JsonContract contract, Type targetType)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateValueInternal(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerMember, Object existingValue)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.SetPropertyValue(JsonProperty property, JsonConverter propertyConverter, JsonContainerContract containerContract, JsonProperty containerProperty, JsonReader reader, Object target)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.PopulateObject(Object newObject, JsonReader reader, JsonObjectContract contract, JsonProperty member, String id)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateObject(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerMember, Object existingValue)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateValueInternal(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerMember, Object existingValue)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.SetPropertyValue(JsonProperty property, JsonConverter propertyConverter, JsonContainerContract containerContract, JsonProperty containerProperty, JsonReader reader, Object target)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.PopulateObject(Object newObject, JsonReader reader, JsonObjectContract contract, JsonProperty member, String id)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateObject(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerMember, Object existingValue)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateValueInternal(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerMember, Object existingValue)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.Deserialize(JsonReader reader, Type objectType, Boolean checkAdditionalContent)
at Newtonsoft.Json.JsonSerializer.DeserializeInternal(JsonReader reader, Type objectType)
at Newtonsoft.Json.JsonSerializer.Deserialize[T](JsonReader reader)
at Microsoft.PowerBI.Packaging.PowerBIPackagingUtils.DeserializeSettingsJson[T](JObject jsonContent)
at Microsoft.PowerBI.Packaging.ReportSettingsUtils.TryDeserializeReportSettings(IStreamablePowerBIPackagePartContent streamablePowerBIPackagePartContent, Version pbixFileVersion, ReportSettingsContainer& reportSettingsContainer)
at Microsoft.PowerBI.Client.Windows.Services.ReportFactory.DeserializeReportSettings(IStreamablePowerBIPackagePartContent streamablePowerBIPackagePartContent, Version pbixFileVersion)
at Microsoft.PowerBI.Client.Windows.Services.PowerBIReportPartReader.ReadSection[T](StorageSection section, Func`1 func)
at Microsoft.PowerBI.Client.Windows.Services.PowerBIReportPartReader.d__2.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.PowerBI.Client.Windows.Services.ReportFactory.d__2.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.PowerBI.Client.Windows.Services.PowerBIPackagingService.d__4.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.PowerBI.Client.Windows.Services.TemplateManager.d__18.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.PowerBI.Client.Windows.Commands.ApplicationCommands.DataImportCommands.d__41.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.PowerBI.Client.Windows.IExceptionHandlerExtensions.d__1.MoveNext()

Stack Trace Message:
Error converting value {null} to type 'System.Boolean'. Path 'ReportSettings.UserConsentsToCompositeModels', line 1, position 55.

Invocation Stack Trace:
at Microsoft.Mashup.Host.Document.ExceptionExtensions.GetCurrentInvocationStackTrace()
at Microsoft.Mashup.Client.UI.Shared.StackTraceInfo..ctor(String exceptionStackTrace, String invocationStackTrace, String exceptionMessage)
at Microsoft.PowerBI.Client.Windows.Telemetry.PowerBIUserFeedbackServices.GetStackTraceInfo(Exception e)
at Microsoft.PowerBI.Client.Windows.Telemetry.PowerBIUserFeedbackServices.ReportException(IWindowHandle activeWindow, IUIHost uiHost, FeedbackPackageInfo feedbackPackageInfo, Exception e, Boolean useGDICapture)
at Microsoft.Mashup.Client.UI.Shared.UnexpectedExceptionHandler.<>c__DisplayClass14_0.b__0()
at Microsoft.Mashup.Client.UI.Shared.UnexpectedExceptionHandler.HandleException(Exception e)
at Microsoft.PowerBI.Client.PowerBIUnexpectedExceptionHandler.HandleException(Exception e)
at Microsoft.PowerBI.Client.Windows.Utilities.PowerBIFormUnexpectedExceptionHandler.HandleException(Exception e)
at Microsoft.PowerBI.Client.Windows.IExceptionHandlerExtensions.d__1.MoveNext()
at System.Runtime.CompilerServices.AsyncTaskMethodBuilder.Start[TStateMachine](TStateMachine& stateMachine)
at Microsoft.PowerBI.Client.Windows.IExceptionHandlerExtensions.HandleAwaitableAsyncExceptions(IExceptionHandler exceptionHandler, Func1 asyncFunc) at Microsoft.PowerBI.Client.Windows.Commands.CompositeCommand1.Execute(ICommand command, Object parameter)
at Microsoft.Practices.Prism.Commands.CompositeCommand.Execute(Object parameter)
at Microsoft.PowerBI.Client.Windows.Commands.CompositeCommand1.Execute(T parameter) at Microsoft.PowerBI.Client.Program.<>c__DisplayClass6_2.<<RunApplication>b__7>d.MoveNext() at System.Runtime.CompilerServices.AsyncTaskMethodBuilder.Start[TStateMachine](TStateMachine& stateMachine) at Microsoft.PowerBI.Client.Program.<>c__DisplayClass6_2.<RunApplication>b__7(MainWindow mainWindow) at Microsoft.PowerBI.Client.Windows.MainWindow.<<ActivateMainWindow>b__102_1>d.MoveNext() at System.Runtime.CompilerServices.AsyncTaskMethodBuilder.Start[TStateMachine](TStateMachine& stateMachine) at Microsoft.PowerBI.Client.Windows.MainWindow.<ActivateMainWindow>b__102_1() at Microsoft.PowerBI.Client.Windows.IExceptionHandlerExtensions.<HandleAwaitableAsyncExceptions>d__1.MoveNext() at System.Runtime.CompilerServices.AsyncTaskMethodBuilder.Start[TStateMachine](TStateMachine& stateMachine) at Microsoft.PowerBI.Client.Windows.IExceptionHandlerExtensions.HandleAwaitableAsyncExceptions(IExceptionHandler exceptionHandler, Func1 asyncFunc)
at Microsoft.PowerBI.Client.Windows.IExceptionHandlerExtensions.d__0.MoveNext()
at System.Runtime.CompilerServices.AsyncVoidMethodBuilder.Start[TStateMachine](TStateMachine& stateMachine)
at Microsoft.PowerBI.Client.Windows.IExceptionHandlerExtensions.HandleAsyncExceptions(IExceptionHandler exceptionHandler, Func1 asyncFunc) at Microsoft.PowerBI.Client.Windows.MainWindow.<ActivateMainWindow>b__102_0() at Microsoft.Mashup.Host.Document.ExceptionHandlerExtensions.HandleExceptions(IExceptionHandler exceptionHandler, Action action) at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor) at System.Reflection.RuntimeMethodInfo.UnsafeInvokeInternal(Object obj, Object[] parameters, Object[] arguments) at System.Delegate.DynamicInvokeImpl(Object[] args) at System.Windows.Forms.Control.InvokeMarshaledCallbackDo(ThreadMethodEntry tme) at System.Windows.Forms.Control.InvokeMarshaledCallbackHelper(Object obj) at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Windows.Forms.Control.InvokeMarshaledCallback(ThreadMethodEntry tme) at System.Windows.Forms.Control.InvokeMarshaledCallbacks() at System.Windows.Forms.Control.WndProc(Message& m) at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam) at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg) at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg) at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData) at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context) at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context) at System.Windows.Forms.Form.ShowDialog(IWin32Window owner) at Microsoft.Mashup.Client.UI.Shared.WindowManager.ShowModal[T](T dialog, Func1 showModalFunction)
at Microsoft.PowerBI.Client.Program.<>c__DisplayClass6_0.b__0()
at Microsoft.PowerBI.Client.Windows.IExceptionHandlerExtensions.<>c__DisplayClass3_0.b__0()
at Microsoft.Mashup.Host.Document.ExceptionHandlerExtensions.HandleExceptions(IExceptionHandler exceptionHandler, Action action)
at Microsoft.PowerBI.Client.Program.RunApplication(String[] args)
at Microsoft.PowerBI.Client.Program.Main(String[] args)

PowerBINonFatalError:
{"AppName":"PBIDesktop","AppVersion":"2.123.742.0","ModuleName":"Microsoft.PowerBI.Packaging.dll","Component":"Microsoft.PowerBI.Packaging.PowerBIPackagingUtils","Error":"Newtonsoft.Json.JsonSerializationException","MethodDef":"DeserializeSettingsJson","ErrorOffset":"7","ErrorCode":""}

InnerException0.Stack Trace Message:
Null object cannot be converted to a value type.

InnerException0.Stack Trace:
at System.Convert.ChangeType(Object value, Type conversionType, IFormatProvider provider)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.EnsureType(JsonReader reader, Object value, CultureInfo culture, JsonContract contract, Type targetType)

InnerException0.Invocation Stack Trace:
at Microsoft.Mashup.Host.Document.ExceptionExtensions.GetCurrentInvocationStackTrace()
at Microsoft.Mashup.Client.UI.Shared.FeedbackErrorInfo.GetFeedbackValuesFromException(Exception e, String prefix)
at Microsoft.Mashup.Client.UI.Shared.FeedbackErrorInfo.GetFeedbackValuesFromInnerExceptions(Exception e, Int32 depth)
at Microsoft.Mashup.Client.UI.Shared.FeedbackErrorInfo.CreateAdditionalErrorInfo(Exception e)
at Microsoft.Mashup.Client.UI.Shared.FeedbackErrorInfo..ctor(String message, Exception exception, Nullable1 stackTraceInfo, String messageDetail) at Microsoft.PowerBI.Client.Windows.Telemetry.PowerBIUserFeedbackServices.ReportException(IWindowHandle activeWindow, IUIHost uiHost, FeedbackPackageInfo feedbackPackageInfo, Exception e, Boolean useGDICapture) at Microsoft.Mashup.Client.UI.Shared.UnexpectedExceptionHandler.<>c__DisplayClass14_0.<HandleException>b__0() at Microsoft.Mashup.Client.UI.Shared.UnexpectedExceptionHandler.HandleException(Exception e) at Microsoft.PowerBI.Client.PowerBIUnexpectedExceptionHandler.HandleException(Exception e) at Microsoft.PowerBI.Client.Windows.Utilities.PowerBIFormUnexpectedExceptionHandler.HandleException(Exception e) at Microsoft.PowerBI.Client.Windows.IExceptionHandlerExtensions.<HandleAwaitableAsyncExceptions>d__1.MoveNext() at System.Runtime.CompilerServices.AsyncTaskMethodBuilder.Start[TStateMachine](TStateMachine& stateMachine) at Microsoft.PowerBI.Client.Windows.IExceptionHandlerExtensions.HandleAwaitableAsyncExceptions(IExceptionHandler exceptionHandler, Func1 asyncFunc)
at Microsoft.PowerBI.Client.Windows.Commands.CompositeCommand1.Execute(ICommand command, Object parameter) at Microsoft.Practices.Prism.Commands.CompositeCommand.Execute(Object parameter) at Microsoft.PowerBI.Client.Windows.Commands.CompositeCommand1.Execute(T parameter)
at Microsoft.PowerBI.Client.Program.<>c__DisplayClass6_2.<b__7>d.MoveNext()
at System.Runtime.CompilerServices.AsyncTaskMethodBuilder.Start[TStateMachine](TStateMachine& stateMachine)
at Microsoft.PowerBI.Client.Program.<>c__DisplayClass6_2.b__7(MainWindow mainWindow)
at Microsoft.PowerBI.Client.Windows.MainWindow.<b__102_1>d.MoveNext()
at System.Runtime.CompilerServices.AsyncTaskMethodBuilder.Start[TStateMachine](TStateMachine& stateMachine)
at Microsoft.PowerBI.Client.Windows.MainWindow.b__102_1()
at Microsoft.PowerBI.Client.Windows.IExceptionHandlerExtensions.d__1.MoveNext()
at System.Runtime.CompilerServices.AsyncTaskMethodBuilder.Start[TStateMachine](TStateMachine& stateMachine)
at Microsoft.PowerBI.Client.Windows.IExceptionHandlerExtensions.HandleAwaitableAsyncExceptions(IExceptionHandler exceptionHandler, Func1 asyncFunc) at Microsoft.PowerBI.Client.Windows.IExceptionHandlerExtensions.<HandleAsyncExceptions>d__0.MoveNext() at System.Runtime.CompilerServices.AsyncVoidMethodBuilder.Start[TStateMachine](TStateMachine& stateMachine) at Microsoft.PowerBI.Client.Windows.IExceptionHandlerExtensions.HandleAsyncExceptions(IExceptionHandler exceptionHandler, Func1 asyncFunc)
at Microsoft.PowerBI.Client.Windows.MainWindow.b__102_0()
at Microsoft.Mashup.Host.Document.ExceptionHandlerExtensions.HandleExceptions(IExceptionHandler exceptionHandler, Action action)
at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor)
at System.Reflection.RuntimeMethodInfo.UnsafeInvokeInternal(Object obj, Object[] parameters, Object[] arguments)
at System.Delegate.DynamicInvokeImpl(Object[] args)
at System.Windows.Forms.Control.InvokeMarshaledCallbackDo(ThreadMethodEntry tme)
at System.Windows.Forms.Control.InvokeMarshaledCallbackHelper(Object obj)
at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Windows.Forms.Control.InvokeMarshaledCallback(ThreadMethodEntry tme)
at System.Windows.Forms.Control.InvokeMarshaledCallbacks()
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
at System.Windows.Forms.Form.ShowDialog(IWin32Window owner)
at Microsoft.Mashup.Client.UI.Shared.WindowManager.ShowModal[T](T dialog, Func`1 showModalFunction)
at Microsoft.PowerBI.Client.Program.<>c__DisplayClass6_0.b__0()
at Microsoft.PowerBI.Client.Windows.IExceptionHandlerExtensions.<>c__DisplayClass3_0.b__0()
at Microsoft.Mashup.Host.Document.ExceptionHandlerExtensions.HandleExceptions(IExceptionHandler exceptionHandler, Action action)
at Microsoft.PowerBI.Client.Program.RunApplication(String[] args)
at Microsoft.PowerBI.Client.Program.Main(String[] args)

Snapshot Trace Logs:
C:\Users\LU\AppData\Local\Microsoft\Power BI Desktop\FrownSnapShot44756570-557b-47b7-b81b-a79fe4c9f2fe.zip

Model Default Mode:
Empty

Model Version:
PowerBI_V1

Performance Trace Logs:
C:\Users\LU\AppData\Local\Microsoft\Power BI Desktop\PerformanceTraces.zip

Enabled Preview Features:
PBI_b2bExternalDatasetSharing
PBI_sparklines
PBI_scorecardVisual
PBI_NlToDax
PBI_fieldParametersSuperSwitch
PBI_setLabelOnExportPdf
PBI_dynamicFormatString
PBI_oneDriveSave
PBI_oneDriveShare
PBI_newCard
PBI_buttonSlicerAuthoring

Disabled Preview Features:
PBI_shapeMapVisualEnabled
PBI_SpanishLinguisticsEnabled
PBI_qnaLiveConnect
PBI_enhancedTooltips
PBI_angularRls
PBI_onObject
PBI_backstageUI
PBI_gitIntegration
PBI_modelExplorer
PBI_daxQueryView
PBI_aiNarrativesVisual
PBI_qnaImproveLsdlCopilot

Disabled DirectQuery Options:
TreatHanaAsRelationalSource

Cloud:
GlobalCloud

PowerBIUserFeedbackServices_IsReported:
True

Formulas:

section Section1;