In both pictures you are not using your heel and lower leg as an anchor and it has slipped back, instead you should concentrate on keeping a straight line from your hip to your heel. I think a lot of the problem in the second pic is that your stirrups look short. In the first picture I think its due to your body being slightly pitched forward ahead of your horses motion and perhaps pinching with your knee.
I like your release in the jumping picture, its short but in no way restrictive. Also YOUR HORSE IS SOOO CLEAN!! I don't know how you got all that white so white!! :)