It seems to have stopped happening for me as well. I was having all sorts of different screens freeze pretty regularly, not just errors on the upload screen, and that doesn’t seem to be happening anymore.
You just need to upload it again.
Same thing has happened to me before. It seem to be caused by combining photos, and then gets stuck sometimes I can move the photos and unstick it, sometimes I loose everything and have to redo :-/
Well if you have 160 photos with detailed locations a metadata, projects, and fields, you don’t want to redo everything!! :-/
Ok you’re right