It would be nice if there’s some kind of error message (notification?) when the sync encounters an error.
The problem is that I/O error messages are mostly soft errors (i.e. they will occur, for instance when mobile network is dropping, but the attempt to sync will be repated and they’re not permanent errors). DAVdroid can’t know whether this is a permanent issue or whether its temporary.
However, I agree that certificate errors should be counted as hard errors (which will be shown).