Play two animations simultaneously using Unity Animator and Spine

Unity Engine
1

How to play two animations at same time using Animator controller and Spine SkeletonAnimator?
First animation will be from Spine.
Second animation - standard unity animation, which moving child gameobject of gameobject with SkeletonAnimator.

Currently I have one controller with two layers. In second layer located my Second animation. Both animations are triggered to play on same Trigger.
As a result, if second layer in controller has Weight = 1, then it cause Key not found exception and First animation is interrupted, but Second animation is playing well, even if Blending is set to Additive

Thanks in advance!

2

You might have better luck asking about Spine on their forum . The devs there are very helpful and fairly quick to respond.