its my opinion that "normally" the doors are fitted rather loose in rv's... but if yours is fitted to tight, it may need to be shaved a bit.
another problem you may have is an abundance of moisture laden air in the rv, which can only be remedied by giving it lots of ventilation to the outside, so that drier air can enter while the damp air exits... and it may take a day or two for the door to shrink back to its previous size....
heat by itself wont dry the air, but only allow the warmed air to hold more moisture.... so there has to be some ventilation to let the warm moist air out of the enclosed space of the RV...