If the humidity is high, then that could be the cause. Also, if you remove the hides, mist the enclosure, then put the hides back, that could also be another cause.
It gets pretty darn humid in the hides when my snakes take a dump or pee in them. When the hides is dripping wet from the inside, very humid in the enclosure, and smells like Sugar Honey Ice Tea, I KNOW my snake has dropped a load or peed. LOL