In the corrective actions it says to run test I16 (encoder count)
It may not be sensing movement correctly and faulting out, internal counter failure.
the encoder is basically a wheel inside and a led sensor , if something goes bad internally in the sensor due to contamination or wear this can happen. There are some other things that can create this problem also. I have sent you something to help you troubleshoot this. check your email.
good luck
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