Switching the application style from windows11 to windowsvista causes menus to be drawn with transparent background.

Using the attached demo app:

• Click "Switch to windows11" -> style updates to windows11 style
• Click "Switch to windowsvista" -> style updates to windowsvista style
• Click on menu item -> menu shows with transparent background

I have tried with Light and Dark modes, and also forcing Dark mode off with the same results.

Note that using windowsvista style as the initial style functions correctly, it's only after using windows11 style and then switching to windowsvista that there's a problem.