We had wasted a bit of time this evening battling with ALS DIFF to FIND_IR.

Note: when the ISC_LOCK does not find IR with DIFF, check that the diff VCO servo is off before spending too much time tuning the offset by hand. It turns out we were battling the servo and getting confused, possibly this happened because DIFF was in the IR_FOUND state, even though the IR was not found.