DavDroid Crashes when adding a nextcloud account
Davdroid crashes when trying to create your nextcloud/opi account to sync Calendar and Contacts (Caldav/Carddav) on an Android phone. Your account can not be saved.
This issue occurred for me when I updated my old opi to the kinguard software and tried to sync the new calendar/contacts using davdroid instead of the old opi apps. I had reused the machine name and admin account for the new install.
This appears to be an issue with the android online account manager not liking having accounts with very similar credentials.
To resolve this, go to the android accounts (settings -> accounts) and delete any old opi accounts.
Delete the the old opi applications
Shutdown and restart the phone.
Hopefully this will resolve the problem.