On my rig, I would leave the park brake off, with wheels blocked and on level ground. Then with the engine off, I would pump the air down to about 30 lbs which is past the buzzer alert and popout stage. Start the engine and see if the system recovers to cutoff pressure and eliminates your symptoms.
It should take about 3 minutes to get to 100 psi.
The above is part of the air brake test required as a commercial driver pre-trip.
Maybe something that simple will override the problem?
1995 CC Magna #5280
C8.3L 300hp Cummins, 31,000lbs