One of our agronomists passed this information along:

I noticed the bolts on both ends of my tailgate cables getting loose, the black one in the picture was bending and I couldn't thread it back in anymore. 3 out of my 4 were atleast somewhat loose.  I talked to another fieldman recently and we found a couple on his pickup as well.  Simply coming from lots of up and down the ATV ramp. 

They are an 8mm x 30 mm metric.  Can't remember what metric size wrench they take, a 1/2" wrench does work on the factory bolt.  It's worth a quick check as you can imagine what happens if it lets go while you're on the ramp and/or breaks off flush in the tailgate or box and you have to get the old one out.  If they stay tight they won't bend, mine has obviously been loose for a while. 

I figured easy fix stop at a chevy dealer and get a new bolt, they have a special bushing type head if you look at you'll see.  They wanted $100 dollars for a kit and didn't have it on hand. They did not offer the bolt alone at that moment.  The kit is probably cables and bolts.  Instead of paying/doing that, I took a regular 8mm bolt and nut and a regular 5/16 washer and made a replacement for now.  (I plan to keep an eye on this but thinking it should be okay)  Hopefully you don't have to mess with that just tighten up and go.