fix: Avoid subscribing to touch scroll events twice

src/Uno.UI/UI/Xaml/Controls/ScrollContentPresenter/ScrollContentPresenter.Managed.cs

@@ -4,6 +4,8 @@
 using Windows.Devices.Input;
 using Windows.Foundation;
 using Uno.UI.Xaml;
+using Uno.Disposables;
+
 
 #if HAS_UNO_WINUI
 using _PointerDeviceType = global::Microsoft.UI.Input.PointerDeviceType;
@@ -56,6 +58,8 @@ public bool CanVerticallyScroll
 
 		private object RealContent => Content;
 
+		private readonly SerialDisposable _eventSubscriptions = new();
+
 		partial void InitializePartial()
 		{
 #if __SKIA__
@@ -71,6 +75,8 @@ partial void InitializePartial()
 
 		private void HookScrollEvents(ScrollViewer sv)
 		{
+			UnhookScrollEvents(sv);
+
 			// Note: the way WinUI does scrolling is very different, and doesn't use
 			// PointerWheelChanged changes, etc.
 			// We can either subscribe on the ScrollViewer or the SCP directly, but due to
@@ -87,16 +93,21 @@ private void HookScrollEvents(ScrollViewer sv)
 			ManipulationStarted += TouchScrollStarted;
 			ManipulationDelta += UpdateTouchScroll;
 			ManipulationCompleted += CompleteTouchScroll;
+
+			_eventSubscriptions.Disposable = Disposable.Create(() =>
+			{
+				sv.PointerWheelChanged -= PointerWheelScroll;
+
+				ManipulationStarting -= PrepareTouchScroll;
+				ManipulationStarted -= TouchScrollStarted;
+				ManipulationDelta -= UpdateTouchScroll;
+				ManipulationCompleted -= CompleteTouchScroll;
+			});
 		}
 
 		private void UnhookScrollEvents(ScrollViewer sv)
 		{
-			sv.PointerWheelChanged -= PointerWheelScroll;
-
-			ManipulationStarting -= PrepareTouchScroll;
-			ManipulationStarted -= TouchScrollStarted;
-			ManipulationDelta -= UpdateTouchScroll;
-			ManipulationCompleted -= CompleteTouchScroll;
+			_eventSubscriptions.Disposable = null;
 		}
 
 		private protected override void OnLoaded()