There was another recent string about that same issue. Ironically, I had noticed mine had come apart about the same time as I was reading it. Rather than taking it to the dealer, I fixed it with clamps, glue and screws and feel confident the repair is done well.
Dan & Christine (and Molly)
2015 GMC Sierra 4WD Crew Cab Short Bed with Max Trailer Pkg
2015 Jayco White Hawk 27 DSRL