At some points you can see through the 3d model with the shader.

[Atix45]

For testing I applied the shader to this character from Genshin Impact. This meant that you could see the back of the mesh in some places. After adding the outline shader a few spots disappeared but a few didn't.

I used the Godot version 4 so maybe I made a mistake by modifying the shader for the new version even thought I don't think this is the case because I didn't changed much.

I am not good at shader programming so is there anyone, who can help me with this problem?
Down here is a image with the faulty spots marked in red: