Same for me (still in January) : can't research mails using the "research function" and other issues with the sound... I regret to have Big Sur, since I do need to easily find my mails. I tried all the techniques to fix the bug, but it does not work on the long term.
Gunter-1991
Users receive reputation points by contributing quality content to the forums.
Posts include post and replies published on the forums.
Post authors can mark replies as Accepted to indicate successful solutions.
Apple Developer Forums admins can mark replies as Apple Recommended to indicate an approved solution