Hi,
Am882 drivers , 68 Volts, KL23H2100-35-4B motors.

I had peak current set to 4.5 then 4.9 Amps, but now I've lowered it to 3.5 Amps for the next cut. I emailed the company to try and find out if 3.5 amps was RMS or Peak, and they said try both and see if the stepper gets hot. At 3.5 Amps it was cold, so I increased to 4.9 assuming the rating was 3.5 RMS..... but the motors got bloody hot to touch ( as in almost could not hold hand on there for more than 3-4 seconds ) !, so I have backed them back to 3.5 for now.

If the motor stalls at low speed ( when reversing direction for example where it is fighting the machine inertia + cut resistance, ) then at low speed no fault is displayed by the AM882, and the motor will pickup position once it decelerates and commands a reverse, or after a couple seconds of being stalled, it will just start moving again and continue to the new incorrect position.

The Motor coupling is definitely not slipping, and there is no binding, so for some reason at times the motor torque required, is too much for the torque output sometimes, and the only factor I could think of is that over time the stepper gets hot, and that in turn reduces torque. So therefore decreasing speed will decrease cut resistance, or decreasing acceleration will decrease the torque required to overcome inertia in a given time period.