I have a question about the hitch mounting system. Inside the frame there are like flat metal pieces. Someone said that the nut that the bolt goes in are attached to it. Because when I took my hatch of, and went to put it back on. 2 of the bolts couldn't screw back on because it like broke due to rust. Can the whole hitch mounting system be replaced with new hardware ? I want to because I'm installing new rear bumper.