Maybe the power of your kite is pulling you off your edge before you normally pop. Try depower the kite abit, veer down wind and then really drive in that heel side edge for the pop... Hope this helps..

From what you have said and the tricks you have described it sounds like you are slipping out a bit on take-off which often happens as the winds get stronger. Sometimes lowering your kite a bit or at least pulling it down a bit during your trick will help. Really what you want to try and do is bury as much edge into the water as you can, because I would say you are sitting a bit flat and not totally following through to the very last second, you're backing off a little early.
It's all practice though, just try a few different things. Also sometimes it's just the day or conditions that aren't helping you.