I have seen there are a number of threads about issues related to moving folders from within LR, so this one could be related indirectly to some of them (or not - who knows).
This is my problem: when I move a subfolder (i.e. a folder not sitting directly on the root of the drive) to another subfolder in a different drive, Lightroom starts a "Moving folder" task and the progress bar appears to reach 100%, but the operation never completes - the progress bar remains at 100%.
If I check with Windows File Explorer, I can see that everything went fine: the folder has been moved, so, the operation has been completed succesfully. But from within Lightroom, I can still see the old location of the folder (and the new one too, as expected) in the Folders panel. It's as if LR didn't realise that the "old" folder isn't there anymore, and is waiting for something that has already happened. Or maybe it's unable to write this change to the catalog, I don't know.
I hope this explanation is clear enough, but just in case, I recorded a 1 minute video showing this: