They were saying in the FT forum that the 510 pin is too short and the deck threads are easy to strip on this version. People were saying that they couldn't catch any threads with their pin and it would just wobble and get pushed in when they put it on their mods, or just fall right off. Yikes. That would be a PITA to fix if that's what's happening with yours.
I hadn't heard about the grub screw, but I heard about a spring. Seems that something in there is so short that it's not making contact, so it needs to be extended somehow
(don't have one to take apart yet, sorry). Pretty sure the Kanger insulator is to keep the pin from wobbling - kinda like the o-ring fix for the KFL - you'd be able to screw it in and torque it without the screw going in too far...assuming you still have working threads.

Kidney Puncher has KFL 510 insulators - I might be getting some of those, just to have around. Or
teflon o-rings (size 003).
Dunno, Roxy. Sounds like a dud to me. Shoot your video and send the sucker back. I think I'm gonna pay the extra that they'll charge me for shipping and swap mine out for the Coppervape (?) version (the one with the glass tank and 3 decks) when it gets here. At least that one has a better pin/insulator. But watch the deck coatings suck.