Probably a big no-no for many sticklers for originality but judicious use of Silkaflex (available from motor and car paint factors in black and white and applied by mastic gun) can work wonders securing trim or panels that have become old or lost some of their fixings and don't secure adequately - you have a 'window' of about ten minutes before it drys to apply between trim, pushing door panel in to place and holding it down securely in place with strips of masking tape untill Sikaflex drys. It only needs 'dabs' of the adhesive to do the job. Remove trim using knife blade. Done carefully its 'invisible. Wear disposable gloves 'coz it aint half sticky.......