There was an issue with the Merry Mayhem mission that moved you to Category 4 if you killed a Cornundacauda Prowler or Stalker. From that point on, kills in your correct category did not award kill points. That issue has now been resolved, and Cornundacauda Prowlers and Stalkers are now safe to hunt.

How do I know that I was affected?

If you were moved to Category 4 when you really belong to another category, then you have been affected.

What should I do if I am affected?

1: Just continue. First talk to Carl Tucker again, and you will be moved to the correct category. Then you just continue from where you were. Online time will count from Dec 26th 00:00 UTC.

2: Start over. You abandon the mission. Then you get the mission again, and start with a clean slate. If you get the mission at some point after Monday Dec 27th 11:00 UTC, your online time will count from Dec 27th 11:00.

In both cases, the event has been extended to Dec 31st 23:59.

What should I do if I am not affected?

If you are not affected by the bug, you don’t have to do anything. The event is still extended to Dec 31st 23:59.

The mission and Carl Tucker says the event ends on Dec 30th 23:59

The mission text could not be updated by the fix. The event ends Dec 31st 23:59, even if the mission text says otherwise.