After the update to 9.3.4 Scrivener crashed almost immediately on starting up. Deleting it and reinstalling seems to have fixed this (for now) unfortunately syncing now no longer brings in my Scrivener files from Dropbox
For future reference, if you run into this problem again, you can fix it by going into Settings.app, under Scrivener, “Reset Scrivener”, and from there, clear the Dropbox sync cash and restart Scrivener.app (if necessary). That should save you considerable frustration.
At the moment we don’t know what is causing this bug, it appears to be deep inside the Dropbox SDK. We don’t ourselves directly work with the cache, but that is obviously where the malfunction occurs. Sorry I don’t have a better answer at this time other than “reset when you see it”.