Itasca electrical issue

What you are describing is very likely a bad ground. Electricity is like water it will find a way. In many cases the path to ground is through another circuit causing very strange behavior. The problem in motorhomes is how they are built and bad grounds are highly likely to occur. All it takes is a little corrosion and you have a bad ground connection. The good news is the fix is easy. Your problems seem to be at the dash. Look around for a wire going from the dashboard frame to the vehicle frame. Alternatively you can just add another ground connection. A clean metal to metal connection is critical. Don’t ground to any of the fuel or exhaust system or any moving parts.