The door we used for the cabin was initially an inside door, out of the elements. We had sanded the entire door and painted it with extreme weather paint. We also installed weather stripping on the inside to seal air gaps. Slowly, around Halloween, the door started to stick, and it kept getting worse.
We found it was rubbing up against the plastic framing we put around the door. We figured that the door was expanding (even though it was getting colder) because of the door taking on moisture. There were visible signs of rubbing on the top of the door frame as well as on the side.
Some sanding for about 15 minutes did the trick. We need to paint it to help seal and protect the door where we sanded it down, but at least you don’t feel locked inside anymore! The door is back to acting like a door!