(putting this here in case someone else hits it and is as puzzled as I was)
Hit a fun new failure mode today with my 3XL+bitsetter
Homed the machine, clicked ok to the “tool change” dialog and then the Z carriage moved above the bitsetter… and CM throws up a “probe failed” error message.
Solution: It turns out that my normal Z probe aluminum block made contact with the frame of my 3XL in its holder via a screw that holds the holder to the frame, and that caused the probe line to be always set… separating the Z probe from the screw made all OK again.