I had the same Dropbox problem, switched to CloudMe, and then reconnected to my Dropbox account when CloudMe was down longer than usual (and hard to contact). The original sync problem w/ Dropbox seems to have gone away.
I should post the rest of this in the DTTG forum, but will mention here as it’s somewhat related… Now every time I open DTTG on my iPhone, Dropbox opens and asks me if I “allow” access. This never used to happen when I synced to Dropbox for many years. And it doesn’t happen on my iPad, so I guess it must be some permission setting that was inadvertently changed on my iPhone. I’ll poke around, but any suggestions would be appreciated! - Jim