Plastic Fenders

I have seen that happen on lots of trailers from the entry level to the high end. When that happened to ours, we took the fender off and used a fiberglass repair kit to reinforce around the hole from the back side. We drilled the holes slightly larger when we replaced them. Because we hadn't caught it before the fender cracked, one had a fairly large crack but was otherwise intact. That repair held for the remaining eight years that we owned that trailer. So far we haven't had to do that on our new one but we do keep an eye on it.