Hello Chen, I linked you the Skeleton Viewer, which is a separate application from the Spine editor, to download and try to test your skeleton.
Just making sure you did it, as you wrote:
Chen Katchko wrote
Yes. everything works perfectly inside Spine.
Which might mean you didn't test it in the application.
PixiJS is a Third party runtime, not maintained by us, so, if in skeleton viewer you see everything correctly, you might want to let them know something is not working properly.