So I split a two-sided cave into separate MPN files. Carved the back using the UCB earlier without a problem.

Flipped the board over to run the second MPN (the front of the carve) on the back of the same board. I had a series of strange errors and weird things (including being unable to get the board to jog to the left after a certain point). Took the board out, checked all the connectors, re-set the 1/8th inch clearance. Swept out machine. Put board in different places on the UCB.

I keep getting the error where after I jog to the forward-most hole on the UCB, the machine can't find the board thickness. The bit goes into the forward-most hole away from the keyboard and touches the outside thing (the part that you glue the dowel into). I sometimes get the error about the sliding plate but it's on the inside of the UCB against the rail closest to the keyboard per the instructions (I believe this is correct---this is what I've been doing all along). Mostly I get caught in a Re-try/Abort loop because the machine can't find the board thickness.

I'm puzzled because I can see the bit touching the dowel-piece. And I just did this the other day, so I can't figure out what I'm doing wrong.

Any assistance is appreciated.