UPDATE: It seems the core problem was when no signal is being received from the distance sensor that function waits indefinitely which causes the watchdog timer to intervene. I reverted back to the original distance sensing code and modified the hardware to allow for the Parallax Ping. The hardware change I made was pretty simple, the Parallax Ping has a shared pin for the trigger and echo. So I put a diode on the trigger pin to protect it from the 5V return and a voltage divider on the echo pin to reduce 5V to 3.3V. (1.3K and 3.3K resistors) This works well and is accurate with no code changes.