Maintenance for the week of January 20:
• PC/Mac: No maintenance – January 20
• NA megaservers for maintenance – January 22, 4:00AM EST (9:00 UTC) - 9:00AM EST (14:00 UTC)
• EU megaservers for maintenance – January 22, 9:00 UTC (4:00AM EST) - 14:00 UTC (9:00AM EST)
Have you tried deleting the quest and picking it up again, or once you've completed then change the group difficulty to vet then back to normal (or the other way if you're wanting to do vet)? This sounds more like a user error, but then again it's possible there is another small bug rolling around.