I am using the Google Photos app on my OnePlus 3 android phone. Each time I open it, Photos starts backing up (e.g. "Backing Up - 734 photos left"). This number will drop by 10 or 20 and then just stop. I have left it for a long time and it never changes. If I then close the app and open again, it will do another 10 or 20 and then stall again. So it is very slow and tedious. I am backing up to Google Drive, which has plenty of free room. Anything obvious I can do to fix?
I have posted on a Google forum but got no replies.