Mission: Kikowani Station
Difficulty: Legendary
The second big hallway’s second door is not opening. I killed all the enemies, and the friendly phantom doesn’t move. I went to the previous loading point and went back to the door that should open, but nothing happens.
And to be as clear as possible: This is the door I mean Halo 3 ODST Legendary Walkthrough: Mission 6 - Kikowani Station - YouTube
I came across this too. If you fire a few banshee bombs at the phantom then it will eventually move forward 
Usually this happens if the phantom gets stuck and becomes invincible. Just try to get last checkpoint and try again. Eventually it will work
Allright, thanks! I’ll give 'em a shot, let’s see what happens.
Edit:
-I already restarted the mission to see if that helps, but nope… Now the first hallway’s big door is not opening.
Looks like the issue is the same as you mentioned that the phantom gets stuck.
Another edit:
-None of these worked for me, so I restarted the mission one more time. And now I magically got through the second hallway’s door.
Still: Thanks for the help folks!