Z over lag

[gls48]

I have a CNC knee mill with an Anilam 3300M control system. We are primarily using it for pattern drilling at the moment. On occasion it will shut down at some random point in a run. It seems to happen most when the quill is feeding into the part, especially when the bit starts to get dull. The message is “Z over lag" or something close to that. I am wondering if the sensor may be dirty of fouled. If anyone has experienced this I would like to know what you found.
Thanks,
George

[dr.carnage]

I was wondering if you ever figured out the problem? I just started experiencing a similar problem on an Anilam 1100, my X-axis jumps around and gives me an "X-Axis Over Lag" error.