It is what it is, a China made product and you can't really expect anything that means quality out of it. I have 2 Vivi Nova tanks, both tanks work on my Provari but one tank doesn't work on my Lavatube 1, why? Because the quality control on them is crap, I compared them side by side and the posts at the bottom are of different lengths, from what you mention I assume it's just one of those quality control things, and you can't avoid them if you're using China made products, that's just the way it is.