Thanks DWCraig now i`ve seen it`s comparatively easy to access, I`ll check that out and make sure it`s tight. Edit: Hallelujia - that fixed it. I wouldn`t have guessed it was that as there seemed to be no give in the main 510 fitting itself, at all. A very hard quarter turn of the nut seems to have solved it though, Thanks Craig ! Edit 2: I have to add, that although it cured the problem, it didn`t do it as I would have hoped. I don`t think the 510 was loose at all, but tightening up the 510 nut has pulled the connector right in, so much so that the base of the atomiser is now touching the top of the device and friction alone against the rubberised coating is holding it still. Rather that hadn`t happened as I would have liked to have kept the top of the device free of wear and scratches from screwing atomisers on & off.