I shifted the router about a bit due to cabling issues when it got close to the left Y axis (was pinching the power cable). This resulted in the spindle lock button being at the worst possible place…oriented directly above a sloped edge of the inside of the dust shoe…the perfect assistant to press the lock button in when the router plunges down for a deeper pass.
Needless to say, it was a nice little light show of sparks when it tried engaging the lock at 22k rpm…