sounds like warped door, need to check with straight edge or pull a string between the ends.
If warped you may be able to remove the edge frame of the door and see if the door can be pushed straight, if frame is bent it may be possible to straighten it placing on blocks and pushing, but be very careful to avoid kink.
If there is internal wood or frame that is bent then one could place blocks in the jamb and push or remove the door.
All of this has some risk and great care needs to be taken
Make small steps and check often to insure step us working and not overdone
Tony & Lori
1989 Country Coach Savannah SE