I notice the QA is backed up by the main tine on yours. I'm guessing this is a 60"? Because mine is 48" (from Gator) and that spot is wide open (mine attach right out at the ends) - and that is a key problem with it, I think. Nothing backing up the main part of the QA plate so a bit of flex and it can pop out - especially if it was loose (up and down) like when I first got mine. I had mine pop out the first time I used it, and then a couple more times, but not so much recently since I fixed the lower latch by getting rid of the slop (gap in the second pic) that was there.
Notice - nothing in front of the orange QA plate. I think it is too unsupported. Plus I have also seen times where brush pokes through and moves the QA levers around a bit. I watch that closely as that could also make it come loose. I agree, there should be more of a "grate" to the back of the unit to keep stuff from poking through.
This is the looseness I saw at first. Way too much gap (~5/16" or so) meant the latches could pop out under stress.
This was the fix from Gator that I did. I welded an additional plate on top to close the gap. It is just tacked in place in this pic. That helped a lot but I don't believe fixed the entire issue. I think there is a weakness in the design, but I'm hearing that nobody else has this problem. I have forks (Virnig - local place) and a bucket (Kubota), neither of which have problems staying put on the QA. That tells me the QA on the tractor is fine.