The M in the error code stands for Master. Master is the right traction motor.
Lift the truck of the ground and check if you get the error. Can also be mechanical issue.
Also check if the error code isn't different turning left or right. During full turn the opposite wheel turns in the opposite way.

When it comes to the steering pot there is an improvement with shim and spring. Don't grease when you replace.

Your steering axle has got an angle sensor to reduce speeds and/or when steered max left-right it will power the drive motor like a differential.
This is normal.
Parameter for the amount of cutback is called curve cutback.
Parameter Steer table should be set at option #1

FO= motor stall, the encoder signal is constantly 0 when max torque is applied to motor. I'd check the motor encoders of the drive motors and do a steering sensor calibration in the vass section.

In some cases the mechanical connection between drive axle and sensor is lost, worth checking that too.