Dense chemical vapor will trigger the LP detector
I have heard of many things in the 10 years I've been in the RV industry and this flatulence idea only makes sense. I have had customers who have sprayed numerous cleaners and hair products that in turn came close to contact the area around the detector and caused it to go off. Even a spill of wine or beer will do it too.
Liquid Propane does contain mercaptan that gives propane that sulphur smell to it.
The only advice is that when your detector goes off, do not disconnect it. Ventilate the area by opening windows and roof vents to alleviate the cause of the detector to go off. You can even wave a towel to speed up the process of dilluting the air around the detector, much like Grandma would do to the smoke detector in the kitchen while she was burning dinner...
When the detector stops alarming, then you can close everything up and sit tight as if the cause was a propane leak, it would go off again. Then, I suggest that you turn off your tanks and try it again. If the alarm goes off again when there is no propane in the system, then either the detector is contaminated or faulty and needs to be replaced.
And like my mother said, if you need to release gas from the rear, it is best to hold it until you reach the restroom...