Sounds like a chassis ground problem.
The electrical ground connection should be through the umbilical harness, but sometimes the pins are corroded or dirty. Try mating and unmating the umbilical a couple of times to clean the pins. If you have contact cleaner, give the umbilical pins a good spray. Alternately, you can use isopropyl alcohol or WD40. However, WD40 will leave an oil residue that will attract dust and dirt; so wipe the excess oil off of the terminals, after spraying.
Sometimes, an intermittent ground may be caused by a poor electrical connection through the trailer ball/hitch. Do you have the trailer connected to your tow vehicle (TV) with the ball carrier and hitch? If you don't have the ball hooked up, this could be the problem. Hook up the trailer hitch, like you are ready to pull out.
Even if the ball and hitch are hooked up, rust and/or dirt/grime on the ball or in the tongue could be preventing a good electrical connection. Try jumping up and down on the TV bumper or tongue of your Airstream. If that doesn't help, jack up the tongue up and off of the ball, thoroughly clean the ball and tongue, grease the ball and hook up the ball and hitch again.
If all else fails, you may need to check the wiring in the 7-pin umbilical connector to make sure a wire hasn't pulled loose somewhere under your TV.
If you still have a problem, post back in this thread again...