We got to the end of the dungeon and the final boss didn’t spawn in a key thus making the dungeon incompletable.
Just did a grimrail depot and last boss didn’t spawn either. We did avoid one pack at the start of the instance so idk if that contributed to the boss not spawning.
Whole party jumped from the train to see if it would reset.
We skipped one add pack at the beginning to the right and needed 2% at the boss.
Possibly that’s why it didn’t spawn? Because there is no way back to that point once you are on the train?
Unfortunately the above post is correct; if you do not have enemy forces completed, the boss won’t spawn. The double Overseer pack at the start of the dungeon which is normally skippable is required to have completion.