We have had a problem (up nothern Illinois) with condensation dripping on smoke detectors, from our conduit in attic. Duct seal or running all conduits into sides usually works. Could be an issue with NM too, device allows different temperatures to mix via air openings in device. Some detectors come with gasket, possibility this is cause? Good luck. Scott. God knows I've been chasing bad smokes around, usually on Friday nights or Sunday!
