Bad Sensor

I put a new sensor in a couple of days ago. About 1/2 the time since, I've had it turned off. Because when it's on, I can't seem to get it to work right. I think I have officially come across my first "bad" sensor.There have been no calibration errors. But time after time I will check and it will be 100 to 150 points off! I will try to reset it and then in 4 or 5 hours I test again and the