I have this same problem. I can land 3's a couple of times but then I start going off axis also. I have tried slowing down my speed approaching the wake, popping more/less, waiting to set my axis to spin. I haven't found the key yet. I'm not a very consistant rider though so maybe that is my problem. I have a guy that rides with me, he doesn't go huge but he is very consistant on his jumps but I haven't found his secret yet.
I'll let you know if I ever figure it out, you do the same.