Backstalling occurs more often in light winds, so it could partially be a technique thing. However, the 2017/2018 Naish lines tend to stretch easily, resulting in longer front lines, making your kite prone to backstall. How often have you used your bar? If you've used it quite a few times, this could be the problem. Naish has officially admitted this issue, and if you go to your local dealer and show them your stretched lines, you get a set of new & better lines, for free.
Check this video from Jesse Richman, explaining what to do if your lines are stretched: https://www.youtube.com/watch?v=k2HlNgBwU0I
My kites were stalling too, so I forwarded this video to my dealer, and was able to swap my old stretched lines for new lines. Pretty neat of Naish to offer this kind of customer service!