That side on shot looks like you're narrow through your hips/pelvis, probably because of your build. I'm not good at the names of human muscle groups, but my guess is you need to work on whichever ones allow you to open your pelvis up more and that loosen your inner thigh, that will let your leg drape more and let your knee relax and come back a bit. At the moment while you have a shoulder - hip - ankle alignment it all looks rather forced and tense which means it won't hold when the horse moves. I want to say relax, but as soon as anyone is told that they tense up even more! Have a stiff drink or two and a giggle? You just look as though you're trying so hard to get it right that you're blocking yourself, so you try harder which makes you tighter etc etc etc. Maybe forget about being right for a little while and concentrate on having fun, if that allows to to relax and soften you may find some/a lot of it corrects itself. And sideways on I definitely think the saddle isn't helping - if you shorten your stirrup you'll be over the flap and even as it is you're being pushed to the back of the saddle while your knee is being lifted away from where you'd like it. I know I said before about trying to shorten your stirrup a hole, but looking from this angle you can't do that in this saddle, and indeed if you have the stability may be better trying to lengthen them to get your knee off the knee roll. But above all else try to stop trying!