Cannot add birthday to a contact on a contact list hosted by NextCloud
I am trying to add a birthday field for one of my contacts. I have a freshly installed PopOS. Contacts 3.36.1, GNOME 3.36.2. I have an existing contact. I click on "Set Birthday" and add a birthday, then click "Done". I see the birthday there. But then I click another contact and come back to the same contact, and the birthday is gone. This procedure produced the following set of warnings.
I can update other fields, like phone number, however, when I edit a phone number on the NextCloud server, I do not see the changes on the Contacts client (I waited 20 minutes, I restarted the client too), but this might be a separate issue.
~$ gnome-contacts
Gtk-Message: 21:34:00.436: Failed to load module "appmenu-gtk-module"
(gnome-contacts:13905): gnome-contacts-CRITICAL **: 21:34:07.639: contacts_fake_individual_set_primary_persona: assertion 'self != NULL' failed
(gnome-contacts:13905): folks-WARNING **: 21:34:07.647: email-details.vala:55: Empty e-mail address passed to EmailFieldDetails.
(gnome-contacts:13905): folks-WARNING **: 21:34:07.652: phone-details.vala:72: Empty phone number passed to PhoneFieldDetails.
(gnome-contacts:13905): folks-WARNING **: 21:34:13.918: url-details.vala:91: Empty URI passed to UrlFieldDetails.
(gnome-contacts:13905): folks-WARNING **: 21:34:13.934: postal-address-details.vala:285: Empty postal address passed to PostalAddressFieldDetails.
(gnome-contacts:13905): folks-WARNING **: 21:34:13.952: note-details.vala:78: Empty note passed to NoteFieldDetails.
(gnome-contacts:13905): folks-WARNING **: 21:34:26.783: postal-address-details.vala:285: Empty postal address passed to PostalAddressFieldDetails.