Cause=>A fluctuation in the measured values has occurred between 2 encoder

zero marks (encoder pulses may have been lost).

– Check for sporadic interruptions (loose contact, e.g. due to cable drag movements)

– For toothed–wheel encoders, check the clearance between the toothed wheel and sensor

– Check the encoder, encoder cables and connectors between the motor and control module

– Check the shield contact, front panel, control module (upper screw)

– Replace the encoder cables or the control module

– Replace encoder

hope this information will help you...

Regards,
Ekalavya