Bugzilla

Since you had to do a repair and assuming I understand correctly and it fixed the problems, you might want to try the latest beta 128.0b1. Unlike the latest 115, it contains a fix for bug 1857450 which may be the reason you needed to repair the folder.
I think this assumes you are using offline store with the nntp account (referred to as "cache" in the bug title).
Note: It seems that when you set up a new nntp account, offline store is turned off by default.
Here's a link to the beta .tar.bz2: https://archive.mozilla.org/pub/thunderbird/releases/128.0b1/linux-x86_64/en-US/thunderbird-128.0b1.tar.bz2
If you want a different locale than en-US, others are there too in the archive.

Since you had to do a repair and assuming I understand correctly and it fixed the problems, you might want to try the latest beta 128.0b1. Unlike the latest 115, it contains a fix for bug 1857450 which may be the reason you needed to repair the folder.
I think this assumes you are using offline store with the nntp account (referred to as "cache" in the bug title).
Note: It seems that when you set up a new nntp account, offline store is turned off by default.
Here's a link to the beta .tar.bz2: https://archive.mozilla.org/pub/thunderbird/releases/128.0b1/linux-x86_64/en-US/thunderbird-128.0b1.tar.bz2
If you want a different locale than en-US, others are there too in the archive.

Edit: re-read your comment 13. I suppose you could say re-creating the account is the ultimate folder repair. Anyhow, still think the beta may prevent future problems and it will be in the upcoming new release (128?).