The switch plates in the newer units snap off. Just be careful that you don't break it!
Once inside, you can unscrew each switch individually and gently pull it toward you to investigate the wiring. Sounds like either the switch is mis-wired, or you have a short or grounding problem.
Since Airstream no longer published manuals that contain wiring diagrams and such, your best shot once it is opened is to call A/S customer service and request a wiring diagram for that switch with color codes indicated, or just find someone in JC that can tell you over the phone.
Let us know how you do...................