Been having the same problems. Sometimes I'll have a really good carto that works well for a week or more. And other times it's just crappy right out of the box. Sometimes it works great for a day or two and something happens to it. I'm getting pretty sick of the inconsistency. I've experienced these problems with both boge and smoktech cartos. Trying to get my hands on some Ikenvapes, but as you already know, you'd probably have a better chance of finding $20 laying in the street.
I've found that if I get a carto working really well in a tank, it'll work really well for one tank worth of juice, but as soon as I refill it, I start to get dry hits. I've found that it's better to not completely fill the tank. Leave an air gap at the top. For some reason my tank refuses to feed the carto when there is no air space in the tank.