DIAGNOSIS: Yeah, this one's common. The gauge on the Genesis II tank scale isn't a precision instrument; it's a simple spring scale. It can get stuck or become inaccurate, especially if the tank sits on it unevenly or the grill is moved around a lot.
FIX: Lift the empty tank off the scale. Manually press down on the scale platform a few times with your hand to work the spring mechanism. Then, place a known full or empty tank back on it. Sometimes this frees it up. For a more accurate check, pick the tank up—you'll quickly feel if it's light.
IF THAT DIDN'T WORK: The scale mechanism itself might be faulty. You can bypass it by just using the old hot water test on the tank itself, or investing in a separate inline pressure gauge.
HEADS UP: Never rely solely on this gauge. Always have a backup tank ready, especially before a big cook.