I recall my colleague facing a similar problem. It was related to general usage of the image for display. She then used a third party opensource to display the image that optimized it.
Believe it was FFImageLoading - GitHub - luberda-molinet/FFImageLoading: Image loading, caching & transforming library for Xamarin and Windows
You would need to scale down your image. Something like:
<Image Source="mypic.png" />
<ffimageloading:CachedImage Source="mypic.png" BitmapOptimizations = true, DownsampleToViewSize = true/>
Believe there would be difference in how Android10 & Android11 is working behind the scenes for this rendering leading to issue in one only.
1. As Dave suggested, also check for any memory leaks or holding on to not needed resources that could be leading to issue.
2. Make sure you have all the components latest & compatible that are part of your project