I haven't had a problem with mine until tonight. Actually went back to a pre-filled carto while I was trying to figure it out. Turns out it was my problem. I ordered replacement heads along with the Nova, and MFF was out of Vision heads and sent replacement heads they said would fit. And they were right. But, initially wouldn't fit in tank. So (dummy that I am) I removed the condom cap that wasn't clearing the tank. Of course, tank kept filling with vapor. Then realized the small protruding pin was not on my original heads. Removed it, capped with condom and I'm happily vaping away again! Just wondering, tho, what is the function of that "pin" on the replacement heads?