Issue with a gear cutting machine with a siemens control, erratic issue with machine going into a feed hold condition with no alarms present. Machine may run for one day or one hour and then fault in the middle of cycle(spindle stays running). Message on control states, wait:feedrate enable missing and program has stopped. All axis's show enabled but there is no movement and no drive faults are present. Axis's will move manually in jog but the machine will not reference or position in any other mode. No programming issues and there is not any signs of drift (control loop issues). NC/PLC archives have also been reloaded. After power down/up or nck reset it is impossible to ref. (no movement) no alarms. Any suggestions would be appreciated.