Loose box on 2010 DC

So when my 2010 DC shortbox was only 2 months old, the box started to rattle. Turns out the fron passenger corner of the box could be lifted up 1/4 inch from where it bolts on! Bo biggie, brought it to the dealer and told them to tighten in back down.
10 minutes later they were done, and I didnt fell the need to inspect their work. At home, bolt and box were soild.

4 months later I go to add extra D rings and go to remove the 2 forwards bolts holding the bed on. The one that the dealer tightend looked weired, as in the bottom of the washer in the bolt wasnt flat with the bed, it looked raised up around the edges as if they tightend the bolt too hard and sucked it down further than it should, dishing the washer.

So I remove the bolt, and there is a piece of plastic (lookes like a spacer) that sits between the box and the frame, and it is all broken into pieces.

I can't find a scematic of the box anywhere, has this happend to anyone? If I got back to the dealer they will say I broke it installing the D-rings... they are like that...

So then I installed the D-rings anyways and it was tight for a while and the box is loose again and rattles. The bolt is tight however. How to fix it? REALLY dont want to pull the box off.

Thanks for input

 

my bolts keep coming loose also. i know when they get loose is when my box starts to make cracking sound

 

Blue thread lock? Maybe even red?