It seems like the issue you're experiencing with the SkeletonRenderSeparator might be related to a null reference exception when trying to access a part's material, which has been addressed in past updates. Ensure that you are using the latest version of the spine-unity runtime, as similar issues have been fixed in recent updates. Additionally, check if the separator slots you have selected lead to any empty parts without attachments, as this could cause the material to be null. If the problem persists, verify that the materials and shaders used are compatible with your Unity version and the Universal Render Pipeline (URP) if applicable.
