It probably doesn't matter this A M but the door faces east and has had plenty of blistering summer sun in those years. Thanks for the information about shrinkage, didn't know that. That also makes me question what foam insulation does in walls with age. This pic was a recent A M shot and the sun still wasn't quite awake.Bottom half of the door gets more battered by heat and therefore expansion and contraction. It is likely the foam has either pulled away along the bottom or shrunk slightly.
After 37 years...you are winning on this deal.
Also...as I said above...the upper part of the door that is shielded from the North sky...will be warmer. The North facing sky actually pulls heat away.