I've got a FANUC 18-T on a Nakamura-Tome TW-20 and the alarm on the screen is "A00.1 Index Parity Check Alarm" and the closest thing I can dig up in my Maintenance Manual 61805E Appendix is 001 TH PARITY ALARM "TH alarm (A character with incorrect parity was input). Correct the Tape.)

This problem occures seldom but when it does all stops!
The operator says "Either in auto or manual, when the tool touches a part and chatters a bit, the alarm occure as if the sensetivity of something is set to high".

Any thoughts or ideas of which way to go on this anyone?