When there’s a quick change in the player’s inputs, blend trees based on any of the speed-based parameters will “snap” to another state. This already doesn’t look very good, but it’s especially bad for avatars using Dynamic Bone. Unless inert is set to 1 AND the root of the dynamic chain is in the same spot between the two states, the dynamic chain will snap to the extreme opposite its current position.
In other games, these kinds of issues are alleviated by damping the animation parameters – either by using the damping arguments of the Animator.Set* methods or doing something custom. Arbitrary scripts aren’t allowed, and Udon and legacy triggers don’t seem to be available for avatars, so I’m at a loss on how to resolve this. I’m hoping that it can be resolved at all since otherwise, I’m not going to get much use out of Dynamic Bone.