While visiting my local body shop, I saw an F150 getting a door replaced. Both the old door and the new door had the trim off and I could see that both doors had a reinforcement plate but the one on the old door was shorter. The plate on the new door extended all the way to the back of the window and slightly upward.

The trim on the old door is 1 piece but the trim on the new door is 2 pieces. Could it be that this new door is the fix for the crack? If anyone has the 2 piece trim and the crack, then I guess this theory is wrong. If not, this may be a way of determining if your door will crack.