Lens won't go on 40D

just bought a used EOS 40D and a Canon EFS 18-135mm lens. Maybe I'm being stupid here but I'm lining the white dots up and twisting but I can only twist about 1/8 of a turn before the lens is so tight on the camera that it won't move any further.

I've looking at both the camera and lens mounts and don't see anything loose screws. I do see this slight bend in the mount but it almost looks like it's supposed to be there. Maybe not...is this piece normally bent or is it supposed to be straight?