I can't get out of the door with my mechs and not sure how to get around this. Was hoping someone knew or is there a bug? Thanks.

If it's the one in Steiner colliseum where you have to bring the rest of your lance, you'll have to physically pilot each one past the door or they'll get stuck. Yes, it's a bug. That map is the buggiest one, in my experience.

If the door's not opening at all, that's also a bug. Those doors are normally proximity-sensitive so maybe that has something to do with it? Have you tried reloading?

It's the one before the Steiner I think and the AI can't go into where I spawned. The door opens I just can't get out. Hopefully this gets fixed soon.

If you're getting stuck in the junk arena spawn, it's definitely a bug. I've been able to get through that door with an Atlas, so it sounds like the map bugged out and you'd have to load from an earlier mission. I've had the new maps load in with insufficient enemy spawns for what I needed to complete the mission, and no matter how many times I re-loaded it would keep happening so I think what you and I might be experiencing is related to how the mission data spawns.