This door just got repaired last week – successfully. I had thought it was warped because it fit snug with the weather strip along its lower edges, but higher up, the door didn't compress the weather strip. You could feel cold air leaking in. But it wasn't warped. The frames were misaligned.
My door has narrow glass light panels installed along either side. Some doors are manufactured so these panels and the door itself are within one frame, while others (mine) are made in three separate frames and assembled on site as its installed. I've now learned how to tell the difference. In the all-in-one frame, there is a single one-piece aluminum threshold that runs full width. In the assembled-on-site doors, the threshold is separated by frame around each panel, resulting in separate pieces of aluminum. I hope that's clear. Here's a photo I found online of the one piece type threshold on a door surrounded by side panels.
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Now imagine the same thing, but with frame that separates the door from the side panels extending far enough so the one piece threshold becomes three pieces. That's what I have.
The door guy recognized that these 3 separate pieces were slightly misaligned, causing the door to fail to fully engage the frame and weather stripping as it closed. He partially dismantled the whole structure until he could adjust the alignment between the three panels (side panel-door-side panel) and their frames. Once he got them lined up and square, he then glued & screwed everything in place. He then mounted new door hard ware. After about 3 hours work, the door closes correctly. It makes a huge difference, and this "tune up" job cost me $350 instead of $2800 for a replacement door
.