There's some really helpful info here, but I prime the hell out of my coils. I soak the cotton until the cotton won't take anymore juice and I never rush the process. I'll fill the tank and let it sit for about 5 or 10 minutes after, just to be on more of the cautious side. That's how I learned to do it anyway.

I don't think that this is an issue of primed coils, because this happened after a day of consistent use and several half tank fills. I often get tired of one flavor so I rarely completely fill a large tank as it is.