Version 2.1.66 (70506aeb)
Python 3.9.15 Qt 6.5.2 PyQt 6.5.2
Use these settings
Go to the Deck Browser or Deck Preview screens, then change Anki’s theme either from Light → Dark, or Dark → Light
(the bug does not seem to occur if you change the theme while in the Reviewer).
Go to the Reviewer: every time you move the mouse cursor over either the top or bottom bar, the bottom bar will “shake”, going first a few pixels down and then back to the original position.