Bindable Property destroying SkiaSharp Rectangle - xamarin.forms

Question

I have a very strange issue. In the following code at 261 in the TouchActioNTypeCancelled i want to call a Method which should set the CroppingRect.Rect to my bindable Property testImage. The Strange thing: When testIamge is a normal Property, not bindable, everything works fine. I can move the croppign rectangle with all corners in the view. If i now change the Proeprty to a bindable property when i start movign the rectangle on one corner in the app i can move the rectangle only from the opposite corners again and if i press the opposite corner, the rectangle buggs back into its original position. I don't understand how this can happen. I did not yet consume the Property in the view since i wanted to check first if it works without consuming it.
This is the way it works with a npormal property. In fact, this is, how i want it to work with a bindable proeprty as well:
Workign example(only with normal property)
This, however, is how it works with the bindable property currently:
Not working example(Bindable property)
public static readonly BindableProperty testImageProperty =
BindableProperty.Create(nameof(testImage), typeof(SKRect), typeof(SKRect));
public SKRect testImage
{
get
{
return (SKRect)GetValue(testImageProperty);
}
set
{
SetValue(testImageProperty, value);
}
}
//public SKRect testImage { get; set; }
void OnTouchEffectTouchAction(object sender, TouchActionEventArgs args)
{
int i = 0;
SKPoint pixelLocation = ConvertToPixel(args.Location);
SKPoint bitmapLocation = inverseBitmapMatrix.MapPoint(pixelLocation);
switch (args.Type)
{
case TouchActionType.Pressed:
// Convert radius to bitmap/cropping scale
float radius = inverseBitmapMatrix.ScaleX * RADIUS;
// Find corner that the finger is touching
int cornerIndex = croppingRect.HitTest(bitmapLocation, radius);
if (cornerIndex != -1 && !touchPoints.ContainsKey(args.Id))
{
TouchPoint touchPoint = new TouchPoint
{
CornerIndex = cornerIndex,
Offset = bitmapLocation - croppingRect.Corners[cornerIndex]
};
touchPoints.Add(args.Id, touchPoint);
}
break;
case TouchActionType.Moved:
if (touchPoints.ContainsKey(args.Id))
{
TouchPoint touchPoint = touchPoints[args.Id];
croppingRect.MoveCorner(touchPoint.CornerIndex,
bitmapLocation - touchPoint.Offset);
InvalidateSurface();
}
break;
case TouchActionType.Released:
case TouchActionType.Cancelled:
if (touchPoints.ContainsKey(args.Id))
{
SetMap();
touchPoints.Remove(args.Id);
}
break;
}
}
private void SetMap()
{
testImage = croppingRect.Rect;
Console.WriteLine("test");
}