Photos stuck uploading 1 item: SOLVED

Hi, this question has been going around for a while and I managed to solve it using all of the techniques in this forum, BUT the one technique that I wanted to share is the easiest and I haven't seen suggested anywhere so here it is.

Simply zoom your photos on your Mac to be 3 photos across, then scan the photos against your iPhone (which is 3 photos across also). You can quickly pick which file is the offender, as the order will change. For me, it was an 11 min GoPro video, and also a PDF file from years ago.

As a secondary check, I'd recommend searching for random file types (PDF, GIF, MP3 etc.)