So... it's the second time it happens, stuck searching Nidhoggur's Guardians all 30 minutes . This time, however, I'm fairly sure I killed all 12 of them (they come in pairs, so whenever I kill one phylla/rhyncho, I immediately search for the other) .
Now that I think about, could it be similar to what happens in OGH, when you kill the 1st/2nd Commander of Destruction with other mobs, and the instance doesn't register the kill?
Also, I noticed some dropped items glitched on the floor: they would not disappear and could not be picked up.
Edited by Asmrow, 24 March 2018 - 05:47 AM.