Regarding the exact version I have installed, from apt search:

thunderbird/jammy,now 2:128.0.1esr~1722554880~22.04~68ae58a amd64 [installed]

I see now that Thunderbird 128.1.0esr was released yesterday. When I looked into the About menu to see if there was a "Check for Updates"-style button, the dialog that came up states:

Thunderbird is being updated by another instance

You are currently on the esr update channel.

Soo ... maybe it's trying to update to the new version and running into some issue?

Possible match to https://bugzilla.mozilla.org/show_bug.cgi?id=1906482

You did not have this problem with version 115?

I did not encounter this problem at all until I upgraded to 128.

The bug you linked to doesn't act the same as my Thunderbird doesn't lock up, it "merely" pegs CPU usage over 100%.

My installed version (via apt) is now at "2:128.0.1esr~1723762298~22.04~fd196ef amd64 [installed]" per apt search, and the problem remains but appears to be less prevalent.

I can make the CPU peg by deleting an email message. Before I deleted, my cpu usage was at about 36% per top and the little activity indicator at the top right of Thunderbird was active. After deleting, in a few seconds the cpu usage per top peaked over 100%, then dropped down again to the mid-50's.

Confirming that this issue stil exists in Thunderbird 128.5.2esr (64-bit), and can be triggered simply by deleting an email that has not been read. I've noted that other folks have reported slowness on deletion as well. Further to that, I have my Trash settings left at default so my Trash folder has a month's worth of stuff in it and my inbox has just under 2500 messages in it, 11 unread.

Is there any progress on this issue?

How many messages in Trash folder?

Have you looked at the list of items at https://wiki.mozilla.org/Thunderbird:Testing:Memory_Usage_Problems

Thanks for your reply, Wayne.

I did follow the link, and specifically regarding Diagnosis step 9 my Trash folder is well maintained. It's on a Yahoo account and thus has settings (defined there) that limit the age of trash and auto-delete old stuff. There are currently 577 emails in that folder .. not a huge amount.

I did run Thunderbird in Troubleshoot Mode and observed the same high-cpu usage when deleting an email from Yahoo. I then deleted another email from another account (270 or so emails in it's Trash folder) and saw the same (but not as bad, 60% cpu instead of 100+) for a minute or so.

Poking at this doesn't make it happen reliably, unfortunately. Typically when only an individual email or two are deleted, things seem to settle back to a decent (low) CPU usage within a minute or so. When multiple emails get deleted in rapid succession, it seems to be worse. I've had the CPU usage peg for minutes at a time, causing the fans on my laptop to roar and it doesn't seem to stop for several minutes. By this time, I'm used to simply exiting and restarting Thunderbird when I hear the fans kick in, and that calms things down. It's not ideal, but it does work!