I have some trouble with ushiro/twister side, and a little bit in the turtle position, but my problems are mostly strategic...
I don't go for subs often enough and aggressively enough, because I am much more concerned with positioning. And while that is not an altogether bad thing, I really need to start committing more fully to submissions, especially when I compete in SAMBO. The subs are there, and I know them relatively well, but it's a mix of me not wanting to give up good position and me not wanting to hurt my opponent.