anthropocene

I'm new to 3D and only messed with 2D before. Now I am trying to make a little game (or at least project) to learn. I added a skybox and got a texture from poly haven. This gray seam appeared and I have no idea why. I tried another texture just in case, but that also wasn't the source of the problem

This is the shader code I've got from a tutorial

shader_type sky;
uniform sampler2D skyTexture;
void sky() {
	COLOR = texture(skyTexture, vec2(SKY_COORDS.x + TIME / 500.0, SKY_COORDS.y)).rgb;	
}

Using Godot 4.0.3 stable
Does anyone know what the issue is? Thanks in advance