I seemed like every hood/fender height and curve was different. There are spacer washers all along the fenders and you can change the height and gap with them. This curve difference puts pressure in different areas of each so some bumpers go flat and some don't.
I see, so it seems the shape of the fenders, due to possible wrong spacers may be to blame. I have noticed that the curvature of the left quarter panel does not match the trunk, it kind of sags in the center. I tried to adjust it by loosening up the bolts and it popped up a bit in the center but I guess it must be the same problem like the front fender, incorrect spacer underneath. I bet is best not to mess with this stuff before making it even worse, LOL. Too bad someone at the factory did not catch this.
Oh and yes, I noticed that parts and assembly do not match even on the same car, from side to side. I was making some fiberglass parts and apparently the gaps between panels can be 1/4 inch different from side to side. This is what I noticed on my sills to quarter panel gaps. Too bad I noticed this after molding the parts on the car, LOL...