I have a related issue which I can’t find answers to online.
I’m importing animations from a 3dsmax biped, and when the animation attempts to blend between another animation, it appears that spine_03 (on the mannequin) is “taking the long way” to blend into the animation. In other words, instead of rotation just a tiny distance to return to the animation (think of a use where you’re blending between a punch and an idle or a running animation) the spine rotates in the complete wrong direction giving a really bizarre, exorcist effect where the character’s spine spins around in a the wrong direction.
I’ve managed to patch this up by making the blend duration EXTREMELY short (.01) , but this isn’t much of a fix because then I might as well not be using animation blending at all. The character then snaps between animations which is less than desired behavior.
It seems like it’s related to your problem though, I’m curious if you ever found a solution or cause of the problem. If anybody else can weigh in here, help would be greatly appreciated.