Grrr. first time through this and stuck on "Destroy mechs to overload the system". Destroyed the mechs except the courier - that one's health bar wouldn't go down, but it wasn't attacking me either. Then it disappeared leaving me in an empty room with no way out. 40+ mins later still nothing happened. Gave me time to submit a bug. This did occur around 00:00 UTC, so don't know if that has any bearing on triggering bug.
ETA: Re-entering the instance put me in the corridor leading to the room, so only had to redo starting from appeal to Joon, so whilst annoying, wasn't so bad - I thought I might have had to restart right from beginning