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bug: UI Theme Changing is Broken if there is a <Carousel />

See original GitHub issue

Describe the bug

After bumping Avalonia version from 0.9.12 to 0.10.0 theme changing via window.Styles[0] = new StyleInclude is no longer working properly. E.g. every second time I change the theme, the theme is applied correctly but then someone is resetting the styles, see the GIF below:

ezgif-7-caa9cbcc48e9

Update (28.02.2021)

The errors seem to be coming from the <Carousel /> control. Theme changing works perfectly if I remove the <Carousel />, see https://github.com/AvaloniaUI/Avalonia/issues/5530#issuecomment-787417903 Also a <Carousel /> occasionally throws a KeyNotFoundException, see https://github.com/AvaloniaUI/Avalonia/issues/5530#issuecomment-787050397

To Reproduce

Here is the repro. Steps to reproduce the behavior:

git clone https://github.com/worldbeater/Camelotia.git
git checkout updates (a branch with Avalonia 0.10.0)
Launch src/Camelotia.Avalonia.sln or do cd src/Camelotia.Presentation.Avalonia && dotnet run
Press Switch Theme multiple times

On master (Avalonia 0.9.12) theme changing works fine, on updates (Avalonia 0.10.0) theme changing is broken.

Expected behavior

Theme changing at runtime worked perfectly on Avalonia 0.9.12, so I guess it should work on Avalonia 0.10.0? Or, probably there is a workaround that could help prevent the style resetting after doing _window.Styles[0] = new StyleInclude? Currently using this class and avares for theme loading. Possibly related https://github.com/AvaloniaUI/Avalonia/issues/5509

Desktop (please complete the following information):