Several Times i have been runnign the slay all modifier and a mob behind the door that is locked is the final mob we need to kill first time it was a goblin and another time it was an elite. Has happened multiple times.
Double, triple, and quadruple checking the whole dungeons area and there isn’t a single monster left besides the one behind the door.
Happened to me once. The last monster (red dot) was behind or in the texture of the door to the next section. Untargetable, AoE can’t hit it. I had to abandon this dungeon.
What I think happened is that the mob that explodes into spider died near the door and the spider spawned / was pushed into the door texture. To be safe I’m going to do my best to avoid killing any monster close to the doors blocking sections of the dungeon.
The same thing happened to me last night, and just happened to me right now. I guess I’ll have to start a different NMD 