RottenDog Williams 9211 MPU for High Speed The board was said to have an issue reporting switches 15, 23, 31. Switch matrix issues caused by a fault on the board will affect an entire column or row. The most probably issue that caused the reported behavior is a break in the row 7 daisy chain of switches. Recall that switch wiring will almost never be in the same order as is shown in the switch matrix chart.