On Xiaomi Redmi Note 3 Pro, when you edit the contact, it has the section “imported from”.
It runs MIUI 184.108.40.206 - I don’t know how it relates to your version. But as it is same manufacturer, it might be similar.
It happened to my wife’s phone recently (after MIUI upgrade and/or backup again nuked all Davdroid contacts), and few contacts (with pictures) are duplicated 4 times - “imported from” there lists “google contact”, “DAVdroid Address book contact”, “Viber contact” and “Whatsapp contact”.
There is also the option to “Merge contact”, “Separate” or “Delete 4 contact” below that section.
So far I’ve been too busy fixing other issues, so haven’t tried any of those yet.
Let us know how it goes if you do!
Interestingly, sometimes the number of “imported from” accounts and amount of dupes don’t match (like 3 dupes but 4 accounts listed; or 4 dupes and 3 accounts listed)
Note: duplication happened despite the fact that in “Settings” / “System apps” / “Contacts” / “Configure contact lists” it has ONLY “DAVdroid address book” selected.
But I would guess it is more likely that the problem lies with MIUI (but I’m probably prejudiced to its bloat and other design issues). Or maybe it’s MIUI’s interaction with DAVdroid? MIUI in my experience (fixing wife’s phone once every few weeks) historically was NOT being very happy with DAVDroid and owncloud apps on that phone, even after clicking all the checkboxes not to kill it, not to powersave it, yes allow it to autostart etc… Waiting for warranty to run out, so I can reformat it with LineageOS instead.