Managing a yahoo email account via Thunderbird (158.0) and IMAP - moving large number messages

Not sure where/how to post this, so starting here (and happy to move/amend this posting as appropriate.) 15-Oct-2026 Background: I've got a yahoo ("free") email account for many years, and wish to move the current contents of my Inbox to a folder (on imap, not local). Recently yahoo appears to have moved to "cloud" arrangement internally (not sure, but it appears to be the case.) The problem I'm experiencing (below) I believe may be yahoo's back-end cloud processes getting out of sync with Thunderbird's view of the same activity. Therefore, I'm seeking help on how to accomplish this (=I don't think there is a bug in Thunderbird, rather this is a plea for how to manage yahoo's email service for my account.) Symptom: Moving large number of emails between folders both hosted on yahoo, peers to my inbox on yahoo, using imap - the "export" imap service). Thunderbird says it completes the task, but many (not all) of the moved emails re-appear in yahoo's inbox after a short time, so this makes moving a large (more than a few hundred) emails a *very* laborious process. What I'm trying to do: I wish to move my current inbox (has about 7.5K messages) to an IMAP-hosted folder (same account, etc.,yahoo email would see this folder as a peer to inbox). When I select all of the messages on inbox and tell Thunderbird to move these to the local folder, thunderbird appears to indicate the task was completed. If I move a very small number of emails at a time, that does complete successfully (=thunderbird says task completed, and the moved emails do not re-appear in yahoo inbox.) Thanks for looking at this (long) posting and (particular to moderators) if I've posted this incorrectly or in wrong place, please assist! Dave