My guess is the multi function switch, aka turn signal level, is the problem. It's a common point for controlling both the head lights and turn signals. Could also be a frayed wire coming off the steering column or a loose pin in a connector associated with the same.
Rather than taking it to an RV service center take it to someone who specializes with the chassis such as either a Ford or Workhorse commercial truck service center. A mobile mechanic could also perform the service. A replacement switch is a bit north of $75. Being an intermittent problem it may take a few attempts to repair to pin it down and fix it.