Running latest TW with Contacts Version 5.17.2 (21.04.2) I noticed that around
25% of ma contacts on google is missing.
Tried refreshing the collection, but that did not help.
Finally I deleted the addressbook and created a new one. Some error messages
occured:
org.kde.pim.akonadiserver: New notification connection (registered as
Akonadi::Server::NotificationSubscriber(0x7fbf4c1bb420) )
org.kde.pim.akonadiserver: Subscriber
Akonadi::Server::NotificationSubscriber(0x7fbf4c1bb420) identified as
"AgentBaseChangeRecorder - 94763683329824"
kf.coreaddons: Trying to attach UI delegate: KIO::JobUiDelegate(0x564c71fc43b0)
to job KJob(0x564c71ff4270) but this delegate is already attached to a
different job KIO::OpenUrlJob(0x564c71fc9520)
kf.calendarcore: Invalid dtStart
kf.calendarcore: Invalid dtStart
kf.calendarcore: Invalid dtStart
kf.calendarcore: Invalid dtStart

(some more....)

kf.calendarcore: Invalid dtStart
kf.calendarcore: Invalid dtStart
org.kde.pim.akonadiserver: Error while handling command DeleteItems on
connection akonadi_google_resource_1 (0x55b7f4780580)
org.kde.pim.akonadicore: Deleting items from the akonadi database failed: "No
items found"
org.kde.kgapi: Requested resource does not exist
org.kde.kgapi: Requested resource does not exist
org.kde.kgapi: Requested resource does not exist

(some more as well)

org.kde.kgapi: Requested resource does not exist
org.kde.kgapi: Requested resource does not exist
org.kde.kgapi: Bad request, Google replied ' "Contacts API is being deprecated.
Migrate to People API to retain programmatic access to Google Contacts. See
https://developers.google.com/people/contacts-api-migration." '
org.kde.pim.google: Got error: KGAPI2::ContactFetchPhotoJob(0x562fe53147d0)
"Fehlerhafte Anfrage."

The API change seems to be the issue.....
Reported upstream https://bugs.kde.org/show_bug.cgi?id=439285