Z axis not tracking

Ok, so I apologize if the wording here isn't quite right, but I have been having some weird issues with creating a simple velocity tracker for a VR game, but I have brute force resolved most of them so far.

But I'm kinda stuck on this one: when I rotate my object 90 about Z in the editor and spin it a repeating transform.rotate(new Vector3(x,0,0)) I get rotation about the Global Y as I expect as the local X is now in line with the Global Y. However when I rotate 90 about the Y then do the same repeating transform.rotate(new Vector3(x,0,0)) rather than seeing rotation about the Z, it is still showing rotation about Global X in the script and editor despite the fact that visibly it is rotating about Global Z.

as a result, when I try to calculate the instant linear velocity on impact, I am losing all the X velocity contribution from the rotation about the Z.

Any thoughts?