You need to take this up with your instructor(s), have them watch and coach you.
We can't possibly tell what your mistake is without seeing it.
This is a question that you need to ask your instructor. We cannot accurately correct your technique because we can't see what you're doing wrong. Ask your instructor to get the best feedback.
I'm learning kata Empi at the moment, and I'm struggling. I've pretty much got the pattern down, the thing that's foxing me is the jump. One foot always seems to land before the other, and I always seem to land off-balance and then stumble. Can anyone offer any pointers on how to make the jump less of an obstacle? I've heard about turning the back foot first so you're not actually jumping the full 360 degrees but I don't understand how that works.
(I'm hoping there's an answer other than practise it to death...!)
