Pluto/Hades Ambulas boss fight enemy spawn issue

[DaftTechno]

During the Ambulas boss fight, the door you use to enter the arena seals behind you for the remainder of the mission, but enemies continue to spawn behind that door. In this screenshot you can see close to 20 enemy icons on the mini-map. This leads to a lot of downtime where players are left sitting idle while waiting for more enemies to spawn inside the arena or for the Ambulas timer to count down.