Hi and welcome. Sounds to me like you're having trouble with the wick keeping up on the chain vape. This is not an uncommon problem with store-bought coils. They usually have small wick ports, and there isn't a borking thing you can do about it. Ever considered becoming a coil builder? A good RTA like the Serpent SMM or a good RDTA like the iJoy Limitless, combined with a DTL coil strength and rayon wick will obviate this problem for the most part... Thinner juice might help what you have, but beware throat hit. 12-18 is far greater nic than I'd recommend for DTL, but I suspect it's already pretty harsh and more PG will increase this. And for the nonce, take a sewing needle and jam it into the wick ports to "fluff" the wick when you next install a coil. Sometimes that helps too.