Just had this happen to me, ie the stop dropped back down while hauling a load. Called the dealer and asked if this was supposed to happen, I thought it was broke or I just couldn't figure out how to keep it locked up as a load stop. I checked the owner manual before calling the dealer but nothing mentioned in that either. Has anyone found a solution to this? It would seem like a wedge placed in the channel while its vertical would work. i am surprised no aftermarket product is available.