I've had two coaches. A Vista cruiser and now a tourmaster. On both, the abs Plastic panel where
the parking brake valve is located crumbled! This plastic is not strong enough to handle the pressure exerted to engage and disengage the parking brake!
I have made a new plastic backer with metal stiffiners attached. Very poor design.
Sorry, all put back together. Basically I sandwiched an acrylic sheet to the broken abs plate. This allowed me to contact glue everything back together. I then bridged the opening on either side of the parking brake switch with 2 thin 1" strips of metal to provide some support. Working, so far.