If the router is running and the Z stepper releases there is enough weight and vibration to drop the router into the work piece/work surface. Once the big collet hits you’re likely mere seconds away from smoke and then a few more seconds away from fire. These machines really shouldn’t be left unattended.
Ah, right. I am going to use PSON pin to disengare spindle like forum advised me in another thread. Fire protection and spindle wear-out optinization simultateously.