I had my bow stall all the time until I managed to discover that I actually had the depower too high after around 15 or so sessions (ie front lines too tight).
I think the best method is to place your bar center; so between sheeted in and out and then the make sure that at that point both front and back line tension is roughly equal, do this by adjusting the connection points on the kite and observing the 'sag' in the lines when you fly the kite.
I've got my back lines at the closest connection to the kite so they are as short as possible and my front lines at the furthest so they are as long as possible. Makes a world of difference, the kite responds so much better and powers up more easily, although I have to be careful now not to flare the kite

. I was able to stay up and riding with so little effort... its like a different kite.