Interesting error got today, all was working fine but when I played it several times it started to give me errors. It was OK 1st 2 times I played the scene, and it is ok when I play it in the editor. Here is screen:
The rotation X and Y axis suddenly jumped to NaN.
It may or may not have something to do with interpolation type in use.
Scroll down to “Rotation Interpolation Types” topic to see how that is changed. It seems using Quaternion there is safest way.
Yes Unity rotation animation curves are quite buggy. I have searched the forum and found a lot of issues started with unity 5.3 and some of them manifest itself only on mobile platform. I just skipped it and went back to Spine. Sadly have this kind of problem with other clients work but without the errors, just simple funky rotation behavior.