Hey 343,I used to be a beta tester so I have seen plenty of bad bugs in various titles, but theres one major problem with collision on "Complex" that effectively breaks the game.
Heres my error report in full to help you solve the problem.
Description
On "Complex" on any game type the user can jump through the collision model in the BSP allowing them to get inside the model and exploit its collision to get easy kills and defend against attacks on any game type.
Steps to reproduce
1: Load up "Complex" on any game type.
2: When the level loads proceed to the right hand side of the map.
3: Enter the section near the giant cylinder with the "05" decal on it.
4: Once inside go to the right hand corner.
5: Crouch jump at the section just above the door frame.
Result
After crouch jumping at the section of roof above the door frame the user was able to get inside the collision model, the user was then able to exploit this in various game types including "Oddball" & "Flood" which seemed to produce the worst results not being able to kill the "Ball Carrier" and not being able to kill "None infected".
Other
Please see youtube video (Sorry for the low quality)
http://www.youtube.com/watch?v=HFsMuleOpgI
