Sequoia 15.7.9 Mail "On My Mac" folders keep closing

Updating to say this seems to only be happening on my Mac mini 2024, but my Mac Studio running the same Sequoia update is NOT having this issue

Is anyone else experiencing or reporting this???

Since the update in the last 2 weeks, my Mail keeps automatically closing my nested On My Mac folders, and the ability to Move mail by clicking the upper "Move" has been pretty much shot.

I use several Macs for work and home, with EXTENSIVE nested folder files for numerous accounting, legal, properties, and life.   Have for 35+ years.  Suddenly the new update has made the folders completely collapse to their basic "over all" folder.   This means I have to sit and manually open each one of these hundreds of nested folders to see where to move and file emails and made the "Move" button blank or basically worthless since it now can only "see" the folders that are open on the sidebar (!)

I operate in POP3 mail not IMAP and don't use things like gmail.  So these things are not in folders on a server but as I want them on my various (numerous) other devices

It doesn't just collapse on Quitting Mail, but even if you keep mail running in the background (which I always do) but it collapses if you just close the Inbox window!  So now I have to keep the mail inbox open and minimized all the time.

I get hundreds of emails daily and have to file the vast majority of them.  This has become extremely prohibitive and ridiculously time consuming (plus I have to remember where previously similar emails were already filed!)

I tried to report it but Apple doesn't even have the pulldown for Sequoia 15.7.9 available - I posted for 15.7.8 but that's not accurate and I have little faith these things go anywhere unless thousand of others report or developers report.

I'd be grateful for any help to solve this.

Thanks!