With introducing of animation culling ability, previously configured authoring prefabs can behave incorrectly. Please, carefully read Animation Frustum Culling section of documentation and make necessary prefab adjustments.
With introducing of skinned mesh renderer bounding box recalculation ability, previously configured authoring prefabs can behave incorrectly. Please, carefully read Renderer Bounding Box Recalculation section of documentation and make necessary prefab adjustments.
RebuildOutdatedBonePoses function was removed from the public accessibility level. AnimationStream will rebuild outdated bone poses automatically on Get calls. It is now derived from an IDisposable interface, and disposal is required after its usage.
The rig definition avatar mask asset is not needed anymore. Prepare your model to contain all necessary information by following the rig definition setup process. All previously created rig definition avatar mask assets can be safely deleted.