I've have sometime seen a odd issues with the maps being tilted a bit on one side or the other. I thought it was just a one time only thing, but it's a see it or not thing that is out there.
Any chance you're playing in 3D? I noticed it gave a slanted feel to some areas in campaign. (I don't use the 3D a lot, as the resolution drop is sometimes pretty noticeable.)
Overpass tilts by design.
Same here on Overpass, it's right when you spawn.
Only tilted map I know is Overpass. Thats the main reason I dont play any type of game on that map