Hello Max,
I figured out why my code is so complicated. I ran allways in situations where I got confusing results or crashes in following nodes. I've tried to solve the problem at the wrong place (the code is now independent of the frame axes length). In a first test I saw that Math.asin in your code gives a NaN in some configurations??? Normally it is impossible, especially when frame.zaxis.x=1. Maybe a bug or a problem with floatingpoint arithmetics??? I don't know???

Karsten