I already reported this bug last week but it still doesn’t seem to be fixed in what I discovered:
Underkeep: 1 group of Nemesis is spawning on top of a spike on the platform leading to the boss. Once spawned it drops through the ground and is no longer in line of sight. Reset by death doesn’t work and makes it impossible to get the crests from full nemesis chest.
Skittering Breach: You can’t get a full kill since 1 group is spawning on a platform that can only be reached by a vortex that is only spawning in 1 particular scenario. If it’s not that scenario you can’t get the full kill hence why you won’t get crests from the nemesis chest because of this.
I had it several times now that this happened, hoping it would be fixed with the reset but it didn’t. I missed out on some crests now because of these bugs. I hope more people will report it and that it will be fixed since every bit of crest is needed in the early weeks of this season.