The main reason so many teams have trouble with 80/20 fasteners sliding loose is beucase... of... well its becuase they used the 80/20 fasteners...
Our team takes steel 1/4-20 bolts and grinds the heads so they can fit in the 80/20 grooves. Then we put a lock nut on the top.
If your're too lazy to grind bolts you could also buy
these.
One heck of a lot cheaper than 80/20, and it will never come loose.
Or you could just put lock-tite on the 80/20 bolts, but thats a pain.