I honestly don't know, Dings. It only happens on one of them, but it's the awesome blue one that I like the most. It somehow pops up, and when I take the chimney off it pulls up like fly-away hair. It's often perfectly clean, even though it tasted like poop, and a quick pop-back-down fixes my vape.
A kuriosity, for sure.
I think that you are sucking too hard. [emoji12][emoji41]