We have a Fanuc 0M controler on a LeBlond Makino, maybe this is just a "blond" problem, but reciently we have had the the spindle starting up on its own.
For example, we may have halted the program, when the spindle has been sent home.
Several times the spindle starts up in the clockwise direction at 1200 rpm and sits there merrily spining away. If we leave it, then eventually it would try to stop, flip about in reverse for a bit, and then wind back up to 1200 again for a while.
If we take the z axis away from the "0" position, the spindle stops immediately.
One time it started up while the tool change arm was wrapped around the cat 50 holder, and that created a few sparks, and lively time for all.

|Basically, there is not running program, it doesn't mater what the next line or existing line commands are, the home led's on the controlller board are flashing as the spiddle is turning, indicating to us that it is able to see the index sensor. There are many adjustable pots on the right side of the board, but without the specific manual to go through step by step adjustments, we are sitting here a little stumpped...