Please remember that stepping motors suffer from age and heat. The strength of the magnets decay. Then you lose the ability for the motor to accelerate as well as cut.
Any drag on the motor will cause it to stall or lose steps. These are open loop systems so the control puts out pulses but cannot verify if the axis achieved position. This is why machines switched to closed loop (position feedback) when it became cost effective.
George
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)