Interesting theory. It's clear that the door has some minute amount of play and that might be enough to create a dicky contact. In the VTC mini those fat spring loaded contacts (almost like fat pogo pins) do provide a good pressure. It was a good design for sure. Right now I'm only using my Primo mini as a fast charger. Coupled with a 2.5A USB wallwart it can charge faster than other mods (close to 2A I think) That's barely "fast" for the large capacity cells we use (less than 1C) so I think it shouldn't affect their cycle life too much (in the RC world many charge up to 4C but that's with packs with extremely low IR values) But apart from that it became unusable with my iHeat in less than two months. Either I screw the attachment fully and it reads over 0.4xxx ohm where the atty is 0.35ohm in reality. Either I don't screw it fully and get the correct resistance reading, but then the attachment is super wobbly (don't know if it's the iHeat 510 threads or the Primo ones but it's loose there is a lot of side to side play) and when I hit it, the pressure of my mouth against the stem is enough to move the atty and the resistance reading jumps all over the place... so it's unusable, at least in TC mode.