This bit can activate only on an axis that is defined as a stepper axis (AXSDEF0). It will also only activates when the ESTALL is enabled. It will activate when the 6K does not see as many encoder counts as it expects to see for the distance that is commanded. The calculation is based upon the Encoder Resolution (ERES) and Drive Resolution (DRES) commands.
If this bit activates only occasionally then the motor is probably hitting high-loads that are causing it to bind, slip or stall.
1) Check and clean the mechanics.
2) Lower the acceleration, deceleration or velocity to make the move less aggressive.
3) Use a larger motor.
If this bit activates right after motion is commanded every time then the system may not be setup correctly.
1) Check the encoder wiring and polarity by turning the motor by hand and checking the encoder counts. Make sure that ENCCNT is enabled and use the TPE command. The encoder should count positive if the motor is turned clockwise when the shaft is pointing at you. It should also give you the same number of counts in one revolution as the ERES is set to.
2) Check the DRES to make sure it matches the drive's resolution.