@TheDoctorII yes, would have been a lot easier if they did…
@henry-nicolas Can you maybe test the new version 0.6.12 (see https://davdroid.bitfire.at/configuration for configuration details) and tell us if it works for you?
The ring tone is not contained in the raw contact. When setting an ring tone in the Contacts app, CUSTOM_RINGTONE of the RawContact is not set (it’s only set for the aggregated contact). See RawContacts docs:
A custom ringtone associated with a raw contact. Typically this is the URI returned by an activity launched with the ACTION_RINGTONE_PICKER intent. To have an effect on the corresponding value of the aggregate contact, this field should be set at the time the raw contact is inserted. To set a custom ringtone on a contact, use the field Contacts.CUSTOM_RINGTONE instead.
So I guess DAVdroid should not synchronize ring tones, as it only aims to synchronize raw contacts.