Those pesky bed rail extensions are ALWAYS breaking. I've through a couple of sets and have been extra carefully in my setups and takedowns. To no avail.

It appears as though the failure comes from the downward pressure on the bed rail. Here is an extension about to fail.

What's the solution? Several people have tried modify the OEM piece so that it won't catch or rub or whatever. It means taking them off, reworking them some way and reinstalling them without any guarantee they will last. The last set of OEM plastic extensions I bought were over $10 each plus shipping. My originals all broke and three of my four replacements have broken. I could have spent another $50 for another new set, modify them some way, and given it another try. Buy why?

Popupmods.com (The Home of the BedWedgie) sells an extension that is heavy cast aluminum and would take some real effort to break, if, in fact, they could be broken. They install exactly as the originals using the same screws and bolts.

They cost $20 each but you'll never have to worry about that part of your tent trailer again.