Quite a few people have been complaining about that on the MVP2's, it appears to be a common problem with them. 
YIKES, Aikanae, you just HAD to mention that, didn't you!!!?? Share the DOOM!
But speaking of Protanks, of which I have a small supply because I decided I never wanted to worry about juice flavors cracking tanks (tho I've still loaded some of the "forbidden" ones into plastic tanks and so far no disasters) ... My stable of PVs is now mostly MVP2.0s 'cause I like them and they do the job. And my Protank IIs absolutely LEAK on them. I was devastated.
THEN last night I saw on a thread somewhere that MVPs are "notorious" for having a low pin connector (I think that's the right term), and that one should use a 510-Ego adaptor on MVP2.0s when using Protanks on them.
Does everyone else with experience already know this, and was it just me stumbling upon one of those key basic facts?
I hope it's correct though because I ordered the adaptors, along with a ton of dripping items, last night. <groan> says my credit card!