YES!
This is the most common reason. The 21i control uses input and output modules. You have a failed output module (shorted) thus the motor keeps going around and around. The modules plug into a backplane. There is no need to remove every wire. The entire terminal strip pulls off the front.
There is also the possibility that a prox switch for tool 1 or tool at pocket could be flaky.
George
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)