Thanks so much for finding this! I've been looking for a good way to do a complete backup before turning in my phone for the recall. I can't do a PC backup because I can't connect to either of my PCs. My Note 4 would never connect and neither will the Note7. I've spent the last three evenings chatting with Samsung Support, all to no avail. It looks like Samsung Cloud might be a good alternative.
BTW, I not only have Gallery backup missing, but Contacts, as well. And am I the only one having problems backing up documents? I checked everything and did a manual backup, and it shows a last-backup time for everything but documents. If I go to the first screen, it displays the error message saying the backup failed.
I also tried unchecking everything BUT Documents and doing a manual backup. It shows 0% complete and that never changes.
I'm only using 14 MB of my 15 GB. Does anybody have any ideas about why this might be happening?