The trailer hitch does not attach to header trailers because it is a ball hitch. I do not know what sort of camera bug that you are experiencing because it has never occurred to me or any of my testers.
Viewing post in FS25 2020 GMC Sierra Denali 2500 comments
Last we checked header trailers were ball hitches - would be very useful if they attached like the vanilla in-game pickup trucks do.
Camera issue might be hard to replicate as others have reported different behaviour - basically going from 3rd to 1st-person view in certain cases the 1st person camera view resets to the middle seat like if it were a tractor, instead of offset to the left behind the steering wheel. Might be a mod conflict but details have been mentioned below in this thread addressing the camera issue.