Im currently building a Hummer Avenger by Italieri or whatever and its a pain in the butt build. the frame is straight but everything else is tilted and i have no idea why. I checked over everything and is all right. so i dont know.

By the looks in your pic there it looks as if the front bumper is drooping to the left a bit, And also look at where the rear of the body attaches to the frame, there are two little pines there that may not be in there right. Its happened to me before on this kit
Vince