mvp 3 help

[maine vapah]

have an issue with my mvp 3 was wondering if anyone else has had issues with the 510 threading stripping out and causing tanks to not sit tight. I have tried multiple tank and none of them sit tight they end up loosening up and causing the ohms to jump all over the place. I have a kanger subtank when it is on tight it reads .6 ohms and it has jumped up as high as 3.6 ohms