But I think we still have this issue:
I just have checked it by myself on one node. A piece for that a upload failed context canceled error has been thrown is sitting happily in its correct destination folder.
If the file has been successfully uploaded which seems to be the case (I mean maybe still it is not successful and it gets later moved to trash or something) then this error is rubbish and completely misleading. In that case it should not be thrown but show a successful upload. Because it is definitely not a failed upload.