@PbG Thanks for sending the reproduction Spine project. While Misaki didn't mention it, we would please also require a minimal Unity project which shows this issue in order to efficiently reproduce this issue. Otherwise there might be Unity project settings differences.
We currently don't know from your postings which exact version of the spine-unity runtime or Spine URP shaders package you're using, or which render pipeline you're using.
When encountering any issues, please in general always ensure to try the latest version of the spine-unity and Spine URP shaders (if using URP) package from the download page, or update the package via the Unity Package Manager window.
