Subviewport is duplicating itself when screen shader is used

[starblinky]

Tested versions

Reproducible in v4.2.2.stable.official [15073af] and v4.3 -dev6 beta

System information

Mac OS Sonoma 14.4.1 (23E224)

Issue description

When using a screen-shader in a SubViewPort there is a double image. The SubViewPort will draw the original texture (pre-shader) and then draw AGAIN with the shader effect on top.

If you select "Transparent Background" the original texture (pre-shader) no longer shows. But now the background is no longer transparent. I can work around this by setting the grey colour alpha to 0 within a shader, but this isn't ideal solution for me.

Steps to reproduce

Shader code:

shader_type canvas_item;

uniform sampler2D tex : repeat_enable;
uniform sampler2D SCREEN_TEXTURE: hint_screen_texture, filter_linear_mipmap;
void fragment() {

	vec4 noiseTex = texture(tex, UV + TIME * 0.2);
	vec4 mainTex = texture(SCREEN_TEXTURE, SCREEN_UV + noiseTex.r);

	COLOR = mainTex;
}

Create a Noise Texture for the shader:

Minimal reproduction project (MRP)

DuplicationBug for Github.zip