you got a bit of what I called 'short pole syndrom'. Really easy to get when going from 14's to 15's. Basically, you start tucking your swing leg into your body to get back faster. You, me, anybody, has to do this on shorter poles (13',14') or they will unbend on you. On longer poles (15'+), you have to have more patience and allow your self to swing all the way through. Once you start tucking that leg into your body, the poles going to start to unbend. You can tell this in the videos real easily by noting that when your leg tucks in, the pole starts lifting you VERY quickly, especially before your hips come up. With a longer, stronger, straighter swing, you'll keep your body and the pole moving (and actually swing your WHOLE body faster, not jsut your foot) and get yourself in better position to REALLY get tossed (annnd get on bigger poles)
So, to get more out of those longer poles: Focus on swinging long and low
(swing down like a gymnist on the bars or rings), and really learn to be patient. Work this especially on your straight pole drills (easiest place to work stuff).
Oh, and don't put "I know what I'm doing wrong" or no one will tell you what your doing wrong