When assembling this puzzle, I had a problem - every now and then one of the squares disappeared. Usually in such cases I save the picture, reload the puzzle and the error disappears. This time I did the same and eventually managed to put together a picture, but I was worried all the time - suddenly the reboot could not and all my efforts spent on this rather complex puzzle would be wasted. Is it possible to do something about this problem, especially since this happens quite often in Belarusian puzzles?
Screenshot with the missing piece: