diff --git a/src/main/java/pro/cloudnode/smp/bankaccounts/POS.java b/src/main/java/pro/cloudnode/smp/bankaccounts/POS.java
index b7f6c6f..ac68717 100644
--- a/src/main/java/pro/cloudnode/smp/bankaccounts/POS.java
+++ b/src/main/java/pro/cloudnode/smp/bankaccounts/POS.java
@@ -26,6 +26,7 @@
 import java.util.Arrays;
 import java.util.Comparator;
 import java.util.Date;
+import java.util.HashMap;
 import java.util.Objects;
 import java.util.Optional;
 import java.util.UUID;
@@ -66,6 +67,8 @@ public final class POS {
      */
     public final @NotNull Date created;
 
+    public final static @NotNull HashMap<@NotNull Inventory, @NotNull POS> activePosChestGuis = new HashMap<>();
+
     /**
      * Create new POS instance
      *
@@ -118,6 +121,15 @@ public POS(final @NotNull ResultSet rs) throws @NotNull SQLException, @NotNull I
         return getLocation().getBlock();
     }
 
+    /**
+     * Get POS chest
+     */
+    public @Nullable Chest getChest() {
+        if (getBlock().getState() instanceof final @NotNull Chest chest) return chest;
+        delete();
+        return null;
+    }
+
     /**
      * Create POS id
      */
@@ -259,10 +271,11 @@ public void delete() {
      * @param pos    The POS
      */
     public static void openOwnerGui(final @NotNull Player player, final @NotNull Chest chest, final @NotNull POS pos) {
-        final @NotNull ItemStack @NotNull [] items = Arrays.stream(chest.getInventory().getStorageContents()).filter(Objects::nonNull).toArray(ItemStack[]::new);
+        final @NotNull ItemStack @NotNull [] items = Arrays.stream(chest.getInventory().getStorageContents()).filter(Objects::nonNull).map(ItemStack::clone).toArray(ItemStack[]::new);
         final int extraRows = 1;
         final int size = extraRows * 9 + items.length + 9 - items.length % 9;
         final @NotNull Inventory gui = BankAccounts.getInstance().getServer().createInventory(null, size, BankAccounts.getInstance().config().posTitle(pos));
+        POS.activePosChestGuis.put(gui, pos);
         gui.addItem(items);
 
         final @NotNull ItemStack overview = new ItemStack(BankAccounts.getInstance().config().posInfoMaterial(), 1);
@@ -304,10 +317,11 @@ public static void openOwnerGui(final @NotNull Player player, final @NotNull Che
      * @param pos    The POS
      */
     public static void openBuyGui(final @NotNull Player player, final @NotNull Chest chest, final @NotNull POS pos, final @NotNull Account account) {
-        final @NotNull ItemStack @NotNull [] items = Arrays.stream(chest.getInventory().getStorageContents()).filter(Objects::nonNull).toArray(ItemStack[]::new);
+        final @NotNull ItemStack @NotNull [] items = Arrays.stream(chest.getInventory().getStorageContents()).filter(Objects::nonNull).map(ItemStack::clone).toArray(ItemStack[]::new);
         final int extraRows = 1;
         final int size = extraRows * 9 + items.length + 9 - items.length % 9;
         final @NotNull Inventory gui = BankAccounts.getInstance().getServer().createInventory(null, size, BankAccounts.getInstance().config().posTitle(pos));
+        POS.activePosChestGuis.put(gui, pos);
         gui.addItem(items);
 
         final @NotNull ItemStack overview = new ItemStack(BankAccounts.getInstance().config().posInfoMaterial(), 1);
diff --git a/src/main/java/pro/cloudnode/smp/bankaccounts/events/GUI.java b/src/main/java/pro/cloudnode/smp/bankaccounts/events/GUI.java
index de2636a..87753f8 100644
--- a/src/main/java/pro/cloudnode/smp/bankaccounts/events/GUI.java
+++ b/src/main/java/pro/cloudnode/smp/bankaccounts/events/GUI.java
@@ -5,10 +5,13 @@
 import org.bukkit.block.Chest;
 import org.bukkit.entity.Player;
 import org.bukkit.event.EventHandler;
+import org.bukkit.event.EventPriority;
 import org.bukkit.event.Listener;
 import org.bukkit.event.inventory.ClickType;
 import org.bukkit.event.inventory.InventoryClickEvent;
+import org.bukkit.event.inventory.InventoryCloseEvent;
 import org.bukkit.event.inventory.InventoryDragEvent;
+import org.bukkit.event.inventory.InventoryMoveItemEvent;
 import org.bukkit.inventory.Inventory;
 import org.bukkit.inventory.ItemStack;
 import org.bukkit.persistence.PersistentDataContainer;
@@ -152,6 +155,34 @@ public void onInventoryClick(final @NotNull InventoryDragEvent event) {
             event.setCancelled(true);
     }
 
+    /**
+     * Detect changes in items of POS chest while a POS GUI is opened and prevent the item change.
+     * POS items can still be modified if no POS GUI is opened for that POS.
+     */
+    @EventHandler(priority = EventPriority.HIGHEST, ignoreCancelled = true)
+    public void posItemsChangeWhileOpened(final @NotNull InventoryMoveItemEvent event) {
+        final @NotNull Inventory source = event.getSource();
+        final @NotNull Inventory destination = event.getDestination();
+        for (final @NotNull POS pos : POS.activePosChestGuis.values()) {
+            final @Nullable Chest chest = pos.getChest();
+            if (chest == null) continue;
+            final @NotNull Inventory chestInventory = chest.getInventory();
+            if (source.equals(chestInventory) || destination.equals(chestInventory)) {
+                event.setCancelled(true);
+                return;
+            }
+        }
+    }
+
+    /**
+     * POS GUI closed
+     */
+    @EventHandler
+    public void posGuiClosed(final @NotNull InventoryCloseEvent event) {
+        if (!POS.activePosChestGuis.containsKey(event.getInventory())) return;
+        POS.activePosChestGuis.remove(event.getInventory());
+    }
+
     public final static @NotNull HashMap<@NotNull String, @NotNull NamespacedKey[]> keys = new HashMap<>() {{
         put("pos-owner", new NamespacedKey[]{BankAccounts.Key.POS_OWNER_GUI});
         put("pos-buyer", new NamespacedKey[]{BankAccounts.Key.POS_BUYER_GUI_CONFIRM, BankAccounts.Key.POS_BUYER_GUI, BankAccounts.Key.POS_BUYER_GUI_CANCEL});