Ah, now some puzzling behavior in my DropBox account makes sense. I was also receiving a constant flow of notifications that various image files had been updated from DropBox. While this plugin reports on my site that it is following my schedule I set for it, and has been successful, I have not actually checked my DropBox to make sure. The behavior your describe would explain what I’m experiencing, and it is not just lately but for quite a while now. I ended up disabling notifications from DropBox as they were driving me crazy. If, indeed, this plugin is doing this on my site I will deactivate it and continue to use BackUpWordPress, which I see is working fine. Only disadvantage is that I would have to manually copy my backup zip to DropBox; not a big deal.
UPDATE just now. I checked my Dropbox and this plugin has not been creating accurate backups, so it must be continuously trying, and that is why I’m getting all those image downloads. Another red flag is that all the links on the info page you get when you click View Details on the Plugins page on your site, you see that most links don’t work and the author’s account has been suspended.
So I will uninstall this and use my other backup. Then can reactivate my DropBox notifications. Whew!