Leaking. That is what the Chevy house said anyway. They were also bent out of shape about "aftermarket brakes..." etc.
I sent the truck in to have the rear brakes worked. They called me with the huge estimate of what it would take to fix it. That included the hose replacement. I told them they could replace the rear shoes, (which is all I had asked for) and that's it.
It is funny how some of the dealers forget the truck belongs to someone besides them.