I’ve had a chance to test the voltages now and as you anticipated they are low with 4 AA batteries. I was getting readings between 4.2 and 4.5V which is apparently enough to not get accurate values from the range-sensor.
I added a 5th battery to the pack and everything “works” properly now.
I put “works” because as @gweimer anticipated there are some issues with my structure of the XOD project. Right now when it turns the range-sensor is not getting a good reading so it continues turning too long. It still needs some debugging and I’ll continue to work on that. I’ll post my results once I get it figured out.