Another place we used to beef up were the direction limits and slow down switches. The cam // switch arrangement on the old US was less than desirable but if you add extra contact blocks to the bottom of the switches not only do you get better spring pressure you can parallel the contacts to double your chances of good connection. This will correct a lot of weird problems. We also would parallel the incoming power connection to the power relay board with wire as the male female connection have a tendency to loose spring tension on the female side. When ever you unplug any boards on a US you should inspect the female side to be sure none of the springs are not flattened out. Then they get hot and can melt in place making a poor connection even worse. I have seen HRV faults caused by individual hall buttons being grounded but the problem only shows up when that button is pressed. We still have about 12 or 14 of these units on service here and they will run quiet reliably but they do have their quirks. Row 4 pin 2 will let you cycle car in test mode.