I pretty much use mini protanks with my mvp 2 and my itaste 3.0. I can't tell if the threads are stripped or if there's just gunky juice in them but they have become hard to screw tanks on. If I get them on, then I can't get them off without it screwing the protank apart which makes it potentially messy. Is there something that someone can recommend trying to clean with? How can I tell if the threads are stripped or if they are just gunked up?