I had this problem. Instead of playing twister with all the hoops to jump through trying to fix the bug, I just formatted the darn thing and re-copied all my music folders back to it. It takes a while for all the folders to transfer but it is a simple solution.
I only use it for music (I can’t imagine watching videos and such on a tiny screen like this but I’m old and do not “text” either) and I keep a mirror folder backup on my PC of what is currently on my fuse.
The USB mode was not the issue, I know what I’m doing there. It was just a silly glitch and this thing gets silly glitches all the time. Like a PC, it needs a fresh start every once in a while.