artic fox 811 on 2005 dodge ram 2500 diesel short bed??

Yeah, post a pic if you can, but that makes no sense. I've run some pretty ugly roads and the camper never wants to slide back, but it will push forward any chance it gets.
Same setup. Rubber mat on painted bed.
2 of your tiedowns need to be pulling forward just a bit. That is probably the issue.
Mine run 2 forward, 2 about straight down.
Now if you were pulling rough trails at a significant uphill incline that may be a different situation than most of us with big campers.