Thunderbird lists sync only one-way to contact groups

[mkraemer0]

I'm using Baïkal 0.8.0 as CardDAV server and in TbSync 2.21 the option "Kontaktgruppen als Thunderbird-Listen synchronisieren" is marked.

When I add lists in Thunderbird 78.10.2 they are synced correctly to the Baïkal server as contact groups.

But when I add with my Android phone via DAVx⁵ a contact group to the Baïkal server it isn't synced to Thunderbird. I've checked with the InfCloud web client that the group is correctly synced to the server.