What I've noticed is that after one up/down cycle of the tongue jack, the TT creeps forward a little bit relative to the truck which causes the jack foot pad to be pulled toward the rear of the trailer maybe up to about an inch. It's hard on the jack mounting plate on the top of the A-frame and you can see the jack jerk back to vertical as the pad is lifted off the ground. Not sure why this happens but it does make it harder for the coupler to let go.
I know someone on this forum who re-enforced his jack so it can't move and am going to do the same thing. Maybe doing this will help the TT stay put. I have to wonder if solidly chocking the wheels will help with unhooking the coupler? Otherwise, putting the TV in neutral is the answer. If on a slope, I'll pull the truck forward a wee bit.