Thanks for your help, it's much appreciated!
If the issue was caused by undo/redo of an action like you suggest (that's not unlikely) then the problem should resolve itself when you completely close and restart Tropy (because at this point the undo history would be cleared). I'm just mentioning this, in case you haven't restarted yet.
Does duplicating other photos work, or is there an issue only with this particular photo? And, by 'uploading', do you mean importing new photos into Tropy? Thanks again!