yes the cat trucks had these P22 blues for sure

usually replacing the directional switch did remedy the problem but there have been other cases where it did not, the problem was in wiring or another component circuit associated with it.

The cat service bulletin mentions all the afore mentioned but also says something about the PDS (presence detection system).

This code can also be generated when the Presence Detection System (PDS) is activated with the seat switch open.

Turn the key switch 'OFF'. Set directional switch to the neutral position. Close the seat switch and apply the hand brake. Turn the key switch back 'ON'. Is the code removed from the display? If yes, you will then clear the code from the Vehicle Control Module (VCM) history folder if one has been set by using The Diagnozer diagnostic program.

I know this does not apply to this Nissan truck with the PDS system or the diagnozer program. It goes on after that to check the transmission input and output signals, if any issues are found there to check wiring, fuses, reverse alarm relay, connector corrosion or bad connections, etc. depending on the nature of the fault seen.

i'm fairly sure the principle is the same on how the system works so maybe it could be the code is hung up in the error history so it may require clearing it out of the ecm after repairing the switch assy.
Normally when repairs are completed these codes will clear themselves but i have seen in some cases where it is persistent and has to be manually cleared using diagnostic software, not even the pedal dance can remove it.

If the Dir switch has been replaced repeatedly and the problem keeps occurring you may want to consider the other reasons this may keep re-occurring. AND... there is always the scenario where if your buying aftermarket parts they might just be poor quality parts. ;o)

SOOO....
this is not so much the computer seeing F&R at the same time, as the computer NOT seeing a signal in neutral, (in these trucks, neutral is not just 'no signal', but is a specific signal for neutral). check for voltage to the switch.

has always been fwd rev lever assembly before
on the cat c5000 line
or the mitsi FCG25N
or the Nissan line

first time I have run into this situation
operator cant now even get it to move now p22 at start up
going to replace fwd rev lever again tomorrow

Is the operating shifting from fwd to rev real fast? That will throw this code at times....you said you replaced switch assy....that should of fixed it....it has in all cases ive run into....code is for ecm seeing fwd and rev selected at same time so is either switch sticking, possible wiring issue or ecm bad....only thing i can think of at the moment