Welcome from another "new guy" here. I have a 1968
The folks here are great and have a vast knowledge of Airstream maintenance issues.
I ran into a similar situation as you...all the electrican worked fine, the outside of the Airstream required a good washing. After washing there were electrical connection issues to deal with.
If everything worked well before, your wiring is fine, you just have an electrical connection problem.Try a spray can product designed for electrical connection cleaning sold at NAPA, Autozone, etc. It will say something to the effect of "electrical contact cleaner". The spray cleans the contacts.
It costs $3 to $6 bucks, spray it thoroughly, no flame or lit cigarette nearby as it will light you up, too. A cheap quick trouble shooting tool.
Good luck. Airstreams are easy to fix, you'll love yours.