Being that I can’t see what is generally happening when you try it, I’m not really sure how to troubleshoot so I will speak on general terms.
This mainly applies when you have landed the trick and understand the mechanics of the trick already but you are trying to become consistent. Consistency generally comes from repetition.
That said, I land tricks that require the most accuracy by making sure that I’m not focusing too hard on aiming. I also find tricks generally much easier to land if I have a certain momentum or rhythm going. Kind of like in basketball where you see the guy dribble a couple times before he takes the free throw shots. Another problem you might be having is committing to the trick. Your body tenses up because you are waiting for that knuckle smash to happen. Firmly establish the motions in your mind, and then commit to completing those motions no matter what when you go to execute those motions. See it happen before you do it.
I don’t know if that will help in any way.