This sounds like it would be related to the GDPR implementation from HQ. We will probably see similar issues in several places the coming months.
Users are allowed to opt-out from being used by third party sites and applications. We therefore only receive partial data on them. It has been hard for us to foresee what the effects would be. We did have a meeting with HQ where they told us their plan, sadly what happened later was not at all what was agreed on, so we were very unprepared.
If you have seen this case on a geocache which doesn't have a lot of found it-logs, it would be interesting to analyze it. But since it will be done manually, I prefer one that don't have hundreds of logs. Even 20 is almost a bit too much.
UPDATE: I wouldn't be surprised if you at some point get an email that you have gotten all those favorite points again, from another user, or even the same. But I don't know yet, that's why we need a case to analyze. The whole GDPR thing is less than a week old.