Yes, that is the latch (4 of them). I am no expert and can only tell you what I think. I think the TM ends pivot (self-leveling) as the end rises and drops.
Thus, after closing the TM and one or more of those latches has been tightened (it's easy because all one has to do is turn a nut in the latch as it hangs loose) out of proportionately to the other latches (the other side or at the opposite end of the TM, then it possibly can cause the middle edge of the bed end or of the couch end (I have a 3326) to pivot up enough to keep the middle hold down latch from catching.
My theory may be wrong, but at least for now, the result appears to be good!:
