I went through exactly the same frame problem and the majority were the crew cab built in mexico and it was all do to frame prep before the wax coating was put on at the factory.I tried going thru customer
service which was a waist of time they just pacify you then I just got fet up and went for the top dog
to get some real results and it worked..
I went thru the same problem with my frame on my 2014 siverado cc sb and the dealer would not do anything so I emailed mary barra she is the top ceo of gm and the truck was taken care of within a weeks time and repaired the right way. [email protected]..