Welcome to iRV2.
Sorry your first post is about problems .
First , " short circuits" in electrical systems , blow fuses or trip circuit breakers ; so your problem is probably power supply to the dash board systems being low due to a poor connection in the chassis battery wiring to the dash, when the head light system draws power , the volts available drop to the point where the electronic systems ( trans shift pad and throttle control ) act up.
Poor dash system ground is possible , but each headlight has a separate ground independent of the dash ground so they shouldn't interfere in the way you describe.
Do you have a multi meter and a 12 volt test light ?
Is your coach on a Freightliner chassis?