Ok mate, did some digging :)
it seems like you have to trigger another bug, bursting out of the wall in the hallway that leads to our "stuck-room".
Just put all of your party members straight in front of the wall and end turn, that should trigger it.
There is also a bug with the final boss, it seems like you have to attack her the very last! first kill everything she summons and the pillars, and once she resummons them or tries to, she is supposed to run away and trigger a cutscene.
OK… the pillar thing is going on endlessly so just do that: Don't attack her at all, clean out the pillars she uses, kill the bugs until none respawn, after no bugs respawn, get one more pillar, and than attack her directly, it worked for me (I did a lot more pillars though) good luck!
I hope this helps.