Since 7.3.0.GA+ I'm seeing an error when calling setRemoteBackup(bool) on an individual File object. "Could not configure remote backup: The file “mydatabase.db” couldn’t be opened." (Setting the flag on a folder works fine,)
Looking at the code in TiFilesystemFileProxy.m around line 570, it appears that the object is setting the flag correctly (on the 'URL'), but then continues to treat the object as a folder, get the contents then output (not throw) an error if no contents are found. (Which a single file will always fail on).
It's not a fatal error, but the code just shouldn't have got that far to output the ERROR message.
A quick fix would be to change the setRemoteBackup method to :