Something is shorting out. I had a flat pack coil...and probably some other related components... go bad in one of my mods and it made crazy things happen. Most notable were ohm readings would bounce all over the place, and now if I put a battery in it, it just fires. I hope my little istick lasts - I just got it and I really like it. It's brushed stainless, too.
I was recently doing research on a small mod and I would agree the evic TC mini is a very good option. And it uses an 18650 unlike its big bro! I couldn't really find any reports of problems with it... I almost got it but went with the Kooopor Plus. I will eventually get the evic mini, though. It seems very solid. If you're chain vaping, you might want to look at something that houses two 18650's or an internal LiPo, though. My little 60W istick is great little mod, so far, but it's really only practical when I can 't chain vape, eg, work. Pioneer4You and Sigelei are good brands, tried and true, in my opinion. VapeNW has the best prices, in some cases much better than FastTech. they sell the evic mini without it's companion tank, so that makes it a bit cheaper. Love that company.