OK, That EMS board is kind of old especially if it is original equipment. With your description of there being an intermittent operation, I would first look for loose or oxidized wires at the connections.
Also, always make sure your coach batteries are good and fully charged, as well as that they have water in them. Remember, your 12-VDC at the batteries should be around 14-5 VDC when they are charging, and around 13.5 VDC when they are fully charged, IF they are only at 12.0 to 12.5 VDC then many of your interior circuit boards will not work properly.
As a side note, you might consider using an external Surge Protector of you can't get your built-in to work properly.