The bolts are jumping from one location in the binding plate to another? That's what it looks like from the pix. Seems to me that would mean that the bolts and washers aren't the right profile for the concave sections in the slots, OR you're not making sure the bolts are sitting right in those concave sections when tightening, OR the bolts don't seat properly in there for some other reason -- like they're too long and bottom out before they form a snug fit. Or maybe there's supposed to be a pad underneath the plate that would increase the height slightly.
These are all just random guesses. But the alternative is that you're so hard on your equipment that you're able to deform the plates enough to have the bindings jump to another position. And you'd think the manufacturer would have heard about that kind of problem if it happened a lot.
In retrospect, "Let's get the goat drunk"
should have been my cue to leave the party.