We ran into this a lot with the P32 chassis. Chevy used a wide meal clamp on the rubber brake hoses. As the hoses aged they tended to swell. The clamp would not let the hoses go out, so they swelled shut. The pressure goes thru OK but will not release when you take your foot off the brake pedal. It is easy to check this. Crank the motorhome, press the brake several times. Extend the jacks until the front tires are off the ground. Stay clear of the motorhome in case the jacks should come down. Try to turn the wheels. They should turn. If not the brakes are staying on. To double check that it is the hose, let the jacks back off and loosen the bleed screws without touching the pedal. There should be no pressure in the hose. If it squirts out, you have pressure in the hose.
1998 Pace Arrow 35 ft. F53 Ford V10 2012 Honda Civic toad
15 year motorhome service manager. 3 popups....2 travel trailers....5 motorhomes....loved them all.