The root cause was probably a manufacturing or installation error. The fix is to replace it.
The O2/AFR is an air-fuel ratio meter that monitors the air–fuel ratio of an internal combustion engine. Also called air–fuel ratio gauge, air–fuel meter, or air–fuel gauge, it reads the voltage output of an oxygen sensor, sometimes also called AFR sensor or lambda sensor. It's designed to ensure the best air-fuel usage for best mileage.