Please find a video of the issue here: https://www.youtube.com/watch?v=jj9nRZC1HCs
If "Offset the menu from the taskbar" is set to "Never" when I try to interact with the Firefox preview window, it instead clicks the icon in the start menu behind the preview window, which, in this case, is File Explorer. Sometimes if I accidentally scroll while moving my mouse/clicking, I might end up launching an app or a game.
To answer your other questions:
1. Windows 11, Version 23H2, OS build 22631.3593
2. Start11 is at Version 2.08