Lousy luck, Sissy! Well, I'll ask what I always ask when something like this happens. Are all three washers installed correctly in the variator? One behind, bevel facing engine. Second goes between pulley faces. Third under the nut.
My brand new variator got grooved right away too. It hasn't caused any problems, though.
Yes, if the driven pulley isn't sliding properly it would cause tension. Mine has never had any issues, though I've suspected it several times, it's always perfect when I disassemble and check it. I notice there IS updated part numbers for the pins and bushings that it slides on (three of each). To check it you have to take off the clutch with involves huge C-clamps or clutch compressing tool and vise. Also a nice big wrench big enough to take off that big nut under the bell. I use a pipe wrench but a nice big adjustable wrench would also work or even a special Kymco wrench. And of course, a clutch holding tool or impact wrench to get the bell nut off.
Lastly, what Axy said! Although I think you've installed a stock belt this time?