Sanctum Ritual Room Resetting Portals

I don't know what's going on, but I've had to retry this room 6 times now and it keeps resetting. I kill all of the mobs, I watch the portal crumble, I go to the next portal, rinse and repeat. I defeat the last mob and the exit is closed. When I walk back to see if any mobs survived, the portals regenerate??? It's obviously broken with no mobs spawning or lichs... https://imgur.com/a/Lo6vYvh