After taking a hit from my eleaf istick 50W with an isub tank there is an occasional hiss after. It lasts for a second or two and then quits. I just replaced the coil and prepped it properly. Could it be a bad coil or is it just more juice burning off?
I know you got an answer already, and I agree with it, but whenever you hear that please please please make sure to verify its not the battery venting. I highly doubt it would vent on that but still, safety first.
Completely unrelated but something to keep in mind below.
I found my builds to do that when they have a high ramp up time and they are getting dry. Since it takes a longer time to heat up and there's hardly any juice left, it starts hissing as it singes the cotton.