So I just experienced this alarm for the first time. It happened at the end of the program shutting down from a 5000 rpm tool path. The alarm popped up and the spindle slowly reduced in speed until it stopped. Anyway I cleared the alarm and started the program again for the new part and after the first tool with it alarmed again but this time give a gear grinding noise like it was changing gears or maybe the spindle lock dog was trying to engage with the spindle still running around 1000 to 1500 rpm.

Any ideas of what me going on?