Each and every folder added to Sync is associated with a database containing all the information about the folder and its contents. When a data fragment from the DB is corrupted and can’t be read properly, the database driver fails to provide access to the data source and thus database error pops up.
This problem may be caused by Sync shutting down incorrectly which, in its turn, can be the result of a system/application crash or an improper/forced shutdown. To avoid incorrect file updates, Sync will suspend synchronization of the folder whose DB is corrupted, whereas the rest of the folders should continue syncing as before.
1) Try quitting and then restarting Sync.
2) Re-add the shared folder to Sync (prior to that, be sure to disconnect and remove the folder from the program).
If this error persists, please, send debug logs to support team though "Help -> Contact Support" menu in Sync app, or collect debug logs manually from peers affected and send them though the web form.