I just updated to Big Sur 11.3 in the hopes that this problem would go away. It didn't. Well, it worked for about a day.
It seems completely random: Sometimes renaming a folder works fine, sometimes it loses just a few files and they eventually come back if I click away from the folder, and sometimes every folder and file is lost and won't come back until I restart Lightroom, and anything in between is also possible. Any scenarios can play out in different ways on the exact same folder of images every time I try to rename it. I've seen no pattern to it. Again, find missing folder/image does nothing when selecting it in the finder. Only thing that works is restarting Lightroom. BTW, I've noticed that Lightoom can successfully point to a missing image if I select "show in finder" (or cmd+r) , so it seems to know how to locate it, but still shows it as missing.
This issue is happening no matter where any catalog file is located, and no matter where any of the images are located, it also happens across operating systems. I have 2 external single USB drives, 1 external 4 bay Raid 0 usb drive, and 3 external 4 bay softraid 0 drives, two are thunderbolt with SSDs. Lightroom resides on my internal SSD. I have also tried running Lightroom Classic from Big Sur OS residing an external SSD, same issue. A few more things to try: clean re-install of lightroom (via creative cloud) on external SSD. Try a catalog file located on internal SSD. New catalog files seems to work for a short while so I may not know if problem returns for a day or two...
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