@DavidWestley - On large, complicated jobs like this, I will chuck a v-bit into the spindle and put a .2" hole at 0,0. THen, if something goes wrong, I can manually move the bit into this hole, nestle it in, and reset x,y zero. REMEMBERING to do this before you start a big job is the hard part. Also, this assumes you are starting 0,0 in a corner and not in the center. Unless you don’t mind a divot in the middle of your piece.
Also, I always screw my work down through the piece into the wasteboard to ensure it does not move until the project is over.
These two things save many of the catastrophic wastes of time during long jobs.