Thanks for the sample.
I compared my code with your sample code.
The differences varied, but ultimately it turned out to be the way the Source was specified.
In your code, it is ImageSource that binds to Source. And in my code, it was a string with Uri set.
When I changed my Source to an ImageSource ... very strangely, everything magically worked.
Is this a bug? Maybe it is.
If necessary, include the above comment in the original bug report.
Anyway, I use ImageSource. I think the priority of bug handling is low.