voltage at the drive motor is only 24v?
should be battery volts
recheck the directional contactors
activate the direction and press the accelerator pedal and use an insulated screwdriver or even your finger, put it on the center insulator and wiggle the movable tips on the contactors, it sounds as if one side is not making on one of them.
the tips may look good but if they are worn down they may not make good enough contact.