I did wonder that too so I turned it off. When I try to load the file I am told something minor is wrong but can be fixed. Then I get this report:
However, it doesn’t fix my particular problem. I think I must give up on this as it must be all about me and I am taking up too much of other people’s time (for which I am nevertheless very grateful).
Actually, I think if I leave it long enough, the beachball does stop but it starts again as soon as I try doing anything.