true, aftermarket parts, especially electrical ones are not up to standards needed, its a roll of the dice when you use them.
I'd say 80% of the time the part fails prematurely or does not work out of the box.
OEM parts are always the way to go ;o)

thx for the update broc_v

We did replace accelerator switch and aftermarket is not appropriate for this application. We ended up replacing with factory accelerator switch and then issue was fixed.

Display shows error 51
Possible cause(s): Improper accelerator pedal linkage, faulty accelerator sensor, faulty main harness, faulty logic unit.

How the error code is triggered:
Accelerator sensor voltage is out of range of 0.2v to 4.8v.
Sensor voltage is 1.41v or more when accelerator switch is opened
Sensor voltage is 0.3v or less when accelerator switch is closed

So either your accelerator linkage on the pedal has moved causing the sensor to go out of range or the sensor itself has a bad spot it's wiper causing the voltage to fluctuate out of range triggering the error. Could also be damaged wires on the harness.

All of the above also applies to the EX models as well ;o)

Good luck

any luck with this?, same issue on a ex5000 but is a hard fault