if this is the CUBE model:
you can check the inching valve for sure but also check the parking brake switch and circuit at the dash controls and make sure it is correctly working, no broken wires etc. Also there may be a switch under the left pedal that operates the brake circuit.
also there is a brake valve associated with this circuit located at the hydraulic tank filter line

If a CB model then there should be a brake valve under the floor plate area (left pedal), it is not an inching valve, its either on or off. This valve is a manual valve that works the brake units on the motor assys releasing them when the pedal is actuated.