first, I always apologize to anyone with an NYK in the USA, and I guess I should for Canada too...do you have a good NYK parts source you could share with the rest of us?

First question, did this problem suddenly happen, (when changing directions?) or has this truck been sitting and you don't have any history? does lift work normally? does it have power steering that works correctly?
My first guesses, (and guesses are all they are at this point, I don't know which NYK control system version this model number uses, off the top of my head, but having directional contactors narrows down the possibilities) would be to check inside the Accel box for switches, and make sure they are operating correctly, and that the cam has not come loose from the shaft (I think there may be a set screw loose and the cam moved so that the wrong switches activate)
When you say "put truck in forward all contactors come" do _all_ the contactors coils energize at the same moment, (including high-speed/bypass and hydraulic pump) and does the same thing happen when you start from a disconnected battery and try rev. first?
Next question, do you know enough about electric motors and controllers to be able to figure out which is the bypass contactor, and does the drive motor run when you (jack the drive wheel off the ground and) manually close (both at same time) one of the directional contactors and the bypass contactor, and do you get the same results (but different direction of rotation) with the other directional contactor?