Thunderbird email problem

FIrst off, I'm aware that Thunderbird does have a forum, but I get no responses whatever over there. I've used Tbird for numerous years  with my W10 PC, and now, with my new W11 PC, with the same issue with each.

Some messages which clearly are not trash, end up in the trash folder, without going to or through the inbox folder. When I try to move them from trash to inbox, they move to the inbox for about 1 second, and then return to the trash folder.

Any ideas? Thanks in advance

Hi, some plausible why's : https://support.mozilla.org/en-US/questions/1362325    Seems maybe IMAP issue.

Note : for info only, no need to download anything : https://recoverit.wondershare.com/email-tips/fix-thunderbird-folder-or-emails-missing.html