I have been using the same 2 carts all week since receiving my riva 510. I am learning the ins and outs, but I seem to be melting/burning the flat sides of my carts. I try my best to place them correctly on the bridge, but I notice I can still twist the cart completely around when placed on the atty. I don't know if it should do this. Am I always putting it on wrong? Should it seat correctly and not turn? I would like to keep my carts as long as possible, and don't want to be vaping plastic (eww!!) What the heck am I doing wrong? Maybe I am over vaping, and over heating the atty, which is quite possible being new to this, and completely quitting analogs, with no natural stopping point, I do tend to over vape.