Then I discovered that when Carousel is installed, the Dropbox app stops automatically uploading photos from your phone. You have to now open Carousel to do so. Broke my existing upload process, and due to iOS permissions for the new app or not launching it frequently or something the new Carousel upload process wasn't reliable.
Discovered this by noticing that weeks of pictures weren't backed up to Dropbox. Glad I didn't lose my phone.
Ended up just deleting the Carousel app rather than figuring it out. The Dropbox app started syncing reliably again.