Disappearing contacts

Many, many contacts missing from my contact list.

However, if a contact calls, the correct name is displayed. If I dial the number ( as I did with a Doctor) the name is displayed. But I can’t search for or find these people in contacts.

Tried erasing all contacts and re-populated from the cloud. That seemed to work for a bit ( at least a week). But now missing again.

Of note, I can specifically identify 2 contacts that went missing/repopulated/ now missing. So it may be that there is something in common with the missing contacts.

Any ideas would be appreciated. Iphone11, up to date iOS, I do not pay for storage.