This repo is a MRE for the issue here: dotnet/wpf#8786
Run the application. The debugger will automatically break twice.
The first break will show the normal behavior (localValue and actualValue will both be {10,10,10,10}).
The second break will show the unexpected behavior (localValue will be DependencyProperty.UnsetValue and actualValue will be {10,10,10,10}).
.NET 7