I am having similar problems. I keep getting duplicates of messages (some duplicated 6 to 8 times), many of the message filters don't work, and it appears to have lost one of my email sources. I've used Thunderbird for over 20 years, and the TB 102 upgrade is the worst problem I've ever had with it. I may have lost my entire history of emails because of this...

I can't understand why Mozilla (TB) developers are not providing any assistance with this widely experienced issue. TB developers need to provide an easy reversion utility to take users back to version 91.11.0 With a LOT of trial and error I was finally able to get my TB back to the old release and things are a lot better now but the process was lengthy and painful trial-and-error on my part.

TB developers: PLEASE step up and provide a fix for the problems that YOU have brought on to many your loyal users.

I was able to find this link that may help some users (no thanks to TB developers)... take a look at this (https://www.reddit.com/r/Thunderbird/comments/vruqlt/how_to_revert_from_102_to_91/) and see if it helps.

I can recall using some of this method to return to TB 91.11.0 but I couldn't get it to import may old profile from an export.. I had to use a copy of the profile created by TB 102 and provide the override parameters (I think it was -p --allow-downgrade).. So, if I am remembering correctly I did the following. (1) Downloaded the 91.11.0 release install package. (2) Make a copy of the 102 profile. (3) uninstall version 102 (4) Install old release (start button-> Run -> copy path to 91.11 exe -> add the -p --allow-downgrade parameters -> hit enter -> when dialog come up, use import from profile (you may get messages about not being able to import all) -> click OK if necessary. (5) cross your fingers. (6) if all goes relatively well, you should be back on the 91.11.0 release and things will start working better. (7) Don't allow any more upgrades to TB