Dragging from imap folder to local folders? Or imap folder to imap folder?

How many messages are being dragged at one time when it fails? How many when it works?

Does it reproduce in Help > Troubleshoot Mode?

This action involves dragging from local folder 'a' to local folder 'b' - no imap or server interaction at all.

I believe the 'chunk' I was moving was in the neighborhood of one hundred messages.

I'll see what results I get in Troubleshoot Mode a little later today when I have time.

Thanks for the reply.

I tried in Troubleshooting mode, and it failed "partially". That is, the messages were moved to the destination folder without remaining also in the source folder (part of the failure mode I overlooked in the initial report). However, some proportion of the moved messages now display the January 20, 1970 date in the list of messages. I can't say how many specifically because there are many duplicates, and with now 526 of 997 messages in the destination folder showing the 1970 date, I'd have to look at each and every one to find out whether they were from the initial failure I reported (which was probably about 300 messages now that I think about it) and this new attempt.

All that said, the only enabled extension I have are:

G-Hub-Pro, an external extension that eases integrating google mail, calendar, etc into tbird as separate tabs. Have used it forever, and it doesn't touch the 'base' message store for tbird. Remove Duplicate Messages, an old extension but one that has proven helpful on occasion (it's how I found the new dupes in the destination folder) Compact Headers, which allows toggling some of the header lines in both preview and full message view.

The compatibility checker reports the latter two extensions as a-okay, and question marks for G-Hub-Pro, which I assume is because it's not from the tbird addon's repository. But since it still happened to some degree even in troubleshoot mode, that should rule out the extensions.

Using the 'Remove Duplicate Messages' extension, it shows duplicates even of the January 20, 1970 displayed messages, but frequently with one copy showing a time of 10:30:41 PM PST and the duplicate showing 10:31.41. The sizes (Header & Body) and number of lines are identical however. I haven't pulled the trigger on removing the dupes though as I don't trust the results.

I dunno. I doubt there's any way to fix this, and I can't think of any mechanism that could correct the displayed 1970 date, as the message headers nowhere show that date.