There is a real good chance your center pin gasket is compressed so much that some of your cartos are not making contact .Send it to me I will replace it . I see this with cartos from time to time rarely with atomizers . In a pinch you can snug your carto down then back off a quarter turn push the center pin up from the inside of the mod and snug the carto back down or like washvap explained you can pull the center pin out a little on the carto . Only try this with the carto on the mod. A gasket in a electronic cigaret is only about 1/16 there is very little room there .It doesn't take long if a person is over tightening atomizer - cartos to compress it to a point there is no longer any spring in the gasket