2005 Volvo tractor brakes not completely releasing

Had a brake issue where the brakes would not completely release, sounded like they had but only 3/4 of the way, all brakes. the shop that had previously worked on it had replaced almost everything, we started from the beginning double checking all hoses and connections, and valves for proper parts and installed in the proper position, hooked up test gauges, knew the issue was the treadle valve but couldn't pin point reason until we were disconnecting the linkage on the pedal the screw that connects the push rod was tight to remove, when we loosened the treadle valve mounting nuts there was a slight release of air from the valves, thought did someone bend something? there is a pedal adjustment on this, just above the treadle valve for your pedal stop, looks like a mounting stud with an Allen center and a lock nut, it was just tight enough to cause all these issues, hope this helps someone,