Has anybody run into this one? I am wondering if it has to do with the clutch cutoff.
Have you checked your pilot pressure? The same pilot pressure that is used for the joystick also releases the park brake.
Can you elaborate a little more about this? I'm assuming you're referring to a Genie GTH-644. As for transmission cut off, the 644/844 does have a de-clutch when the brake pedal is depressed. But I can't think of anything that would make the transmission work only "unless another function is called for". The transmission/drive is totally independent from the machine hydraulics except for the parking brake and brake pedal de-clutch. And all those two things do is take power away from the fwd/rev solenoids of the transmission, not allowing the transmission to engage drive.
I KNOW THIS THREAD IS A LITTLE OLD BUT I HAVE A SIMILAR ISSUE WITH A GEHL RS8-44 W/TRI-FUNCTION JOYSTICK AND PWP PACKAGE. MY ISSUE IS THIS. WHEN YOU FEATHER THE BRAKE WHILE TRAVELING IT TAKES JOYSTICK HYDRAULIC PRESSURE AWAY UNTIL YOU RELEASE THE BRAKE PEDAL OR STOP MACHINE COMPLETELY AND HOLD FIRM PRESSURE ON PEDAL. IT DOES HAVE A DECLUTCH SWITCH BUT MAKES NO DIFFERENCE IF ITS ON OR OFF STILL DOES IT. ANY HELP WOULD BE GREATLY APPRECIATED.