Ahhhh your problem is turning durning a slide attempt? Don't flex youre torso, keep a disciplined boxman,
pull the direction of slide arm & leg in symmetrically.
(slightly) most novices make big ungainly changes, be subtle.
If you can't maintain heading you have a unbalanced airflow problem, get video and see whats sticking out to far and causing the turns. Back in 1994 we had an rather small A lic type that spun on every jump, his rented container was to large-hung over one side...Only way to slow him so other novices could dock was for a D to catch him in a side dock and drop the off side knee. Ill bet you are either flexing the torso or pulling in the arm further than the leg. You should have the proper fitting gear by now but check any add on's like Altimeters or hook knives....it doesn't take much to screw your airflow up man....I've seen experianced RW types backslide because their jumpsuit was unzipped down to their chest strap. You need to get your body and mind together---most probably in your case its a unconcious flex to one side or the other or else your initiating the turn by hand....Video should tell an experianced RW type exactly where the flaw is.
WORK ON IT KID AND IT WILL COME bsbs relax kids, all you need is airtime airtime airtime and the ability to relax of course
Plan your dive and dive your plan bsbs