(this worked on Android 7.1)
On Android 7.1.1 DAVDroid 1.3.4-1-ose , sync creates a bunch of phantom entries below Calendar
Settings - Accounts - DavDroid - [Calendar entry]
I have 3 right now, but I have seen over a dozen
The entries have no title and only display “Sync is OFF”
It does not happen for contacts, only for calendar