Just a thought - could it be the gauge? I would however think that if failing slowly, it would do so with a lower and lower reading, not higher. I had one that sat stuck at 30 when released, and gave me a reading of 110. I finally got a Snap On and read 155. A new cheapo unit read 170. I've read elsewhere that calibration between units is often all over the place, and to pay more attention to balance between cylinders.