A Microsoft file hosting and synchronization service.
I follow in the footsteps of a genius who discovered the workaround. You create a new high level folder (i.e. under OneDrive), name it whatever, then drag all other folders into it. This is easy via ‘select all’. I waited an bit, then dragged them back into their original location - low and behold problem solved. I don’t know how often this process needs to be repeated but so far it’s worked for several weeks. Good luck!