So around here they sell those cartidges that look like filter tip ciggarettes and I never have a problem with those, but when my boss goes to Colorado he brings me ones with a round opening at the top (see attached image). Not all of them look exactly like this, but the ones with a round mouthpiece give me problems. Concentrate starts clogging the mouthpiece and I have to pull on it for a while before it will draw-- then after a while, it gets so bad that I literally end up with prescious concentrate in my mouth! Why does this kind of cartidge do that? Did I screw it up somehow? Is there a way to fix it and reclaim whatever concentrate is polled up in the thing? Buying these is a great deal. They're obviously better and cheaper, but for some reason every time I use one, the mouthpiece gets really gummed up!