I always say, you get what you pay for. Smoktech DCT tanks have notoriously had slidey tanks on their cartos. That's why they designed their tank replacement cartomizers with a flange (which by the way only prevents the carto from sliding towards the battery end of the cartomizer, not off the carto in the other direction).
I never had any luck with the tanks with the black delrin plastic end cap tanks that Smoktech sells. They are "cheap" and were especially slidey, can have quality control issues with poorly fitting pieces, and use a polycarbonate plastic tube which can warp out of shape and crack or melt with certain flavors of juice. I don't recommend these.

<-- No !
I had better luck with the polypropylene tube and metal end cap version like My Vapor Store sells. Overall better parts and a higher quality tank safe to use with all juice flavors, for just a little more money. Complete kit with metal drip tip and 5 pre-punched cartomizers of your choice for under $22.
510 Pro DCTank Combo
If you only want the tank part and can find your own cartomizers and drip tip, you can get this for $9.
Pro DCTank Tube
Another inexpensive option is the polypropylene tubed cartotanks made by Valley View Vapors. These use a silicone grommet in place of the traditionally used end caps (may be more difficult to install and remove the carto in these tanks), but use a juice fill hole/screw which some people seem to like. I'd order some extra screws should you lose one, they're cheap. Just $8 for the tank.
http://www.valleyvapes.com/3ml-Triple-V-Polypro-Tank_p_19.html
The locking Artemis tanks use the polycarbonate plastic tube that some flavors can melt or crack. I've never seen the need for a locking cartotank. A quality-made tank will have proper fitting o-rings which will fit a carto snug enough that it will not slide off. In my 15 months of using
quality cartotanks I've never had a tank slide off of a cartomizer.
BTW, it's common sense not to pick up a PV by the tank, pick it up by grabbing the mod itself, whether it is in a pocket or wherever.