We've had the same problem with ours and I think I've got it narrowed down to Florida humidity. It will light off, in the middle of the night, when it is cool enough that the a/c is not running and that will allow the humidity to build inside the coach and then settle causing the detector told go off. It also happens when the door has been opened and closed a lot with folks going in and out. As we head west on our journeys we hope to find less humidity and maybe less alarms! In the meantime we aim the tower fan we have in the living area at the detector when we go to bed at night and the detector has not gone off since we started doing that.
P.S. I called the manufacturer and they said "maybe humidity would trigger it".
2011 Georgetown 378TS in FireMist
2013 Jeep Wrangler Toad
Kirby the Old Dog, passed but still in our hearts
Max E. Dog, the new pup
Eureka the Old Cat, still hangin' on