I, too, am experiencing frequent Dropbox sync issues, and I also have implemented Bonjour sync with some success. Per this thread, I intend to use both sync processes (Bonjour and Dropbox) in parallel.
Could you outline the cleaning process that fixed Dropbox sync?
From the documentation, I understand that it’s possible to clean a database, or to clean a sync location. Did you specifically clean the database, or did you clean the sync location?