interesting issue with Propane / CO detector

Mine has done the same thing numerous times, with no gas present (shut off at tanks). Yet while lighting a Mr Buddy heater, where I could smell gas before it lit, no reaction from the sensor even though the heater was only a few feet away. They seem to be incredibly sensitive to methane as well (farts, black tank fumes drifting in through the roof vents, fumes from gray tank), anything in a spray can, etc. And in my case, it is always in the wee hours of the morning, when the air is very still. I finally got fed up with it and added a kill switch in the circuit so I can just shut it off, and reset it later. For the record, if propane is on, detector is active.