### Godot version

4.0.2 stable

### System information

issue tested on win10 with ryzen 7 and rx 6600, win11 with ryzen 7 and gtx 3050

### Issue description

When creating a screen reading post processing shader, the normal buffer functions correctly in the editor, but does not seem to be functioning as expected in debug, producing only a solid colour when run. I am unsure if this behaviour is intended, but if so, I feel it should be properly documented.

Running correctly in editor:
![image](https://user-images.githubusercontent.com/71034402/230672620-fc5e4baf-c12e-4755-b7a2-206087459307.png)

Solid colour in debug:
![image](https://user-images.githubusercontent.com/71034402/230672489-d9c29755-c2d3-4e72-9ea0-355148e916fe.png)


### Steps to reproduce

*this shader should be attached to a MeshInstance3D quadmesh*
minimal shader to reproduce:

```glsl
shader_type spatial;
render_mode unshaded, cull_disabled;

uniform sampler2D NORMAL_TEXTURE : hint_normal_roughness_texture, filter_linear_mipmap;

void vertex(){
	VERTEX *= 2.0;
	POSITION = vec4(VERTEX, 1.0);
}

void fragment(){
	ALBEDO = texture(NORMAL_TEXTURE, SCREEN_UV).rgb;
}
```

### Minimal reproduction project

N/A
}
		fade_alpha *= inst->force_alpha * inst->parent_fade_alpha;
		flags = (flags & ~INSTANCE_DATA_FLAGS_FADE_MASK) | (uint32_t(fade_alpha * 255.0) << INSTANCE_DATA_FLAGS_FADE_SHIFT);
		if (p_render_list == RENDER_LIST_OPAQUE) {
			
			if (inst->lightmap_instance.is_valid()) {
				int32_t lightmap_cull_index = -1;
				for (uint32_t j = 0; j < scene_state.lightmaps_used; j++) {
					if (scene_state.lightmap_ids[j] == inst->lightmap_instance) {
						lightmap_cull_index = j;
						break;
					}
				}
				if (lightmap_cull_index >= 0) {
					inst->gi_offset_cache = inst->lightmap_slice_index << 16;
					inst->gi_offset_cache |= lightmap_cull_index;
					flags |= INSTANCE_DATA_FLAG_USE_LIGHTMAP;
					if (scene_state.lightmap_has_sh[lightmap_cull_index]) {
						flags |= INSTANCE_DATA_FLAG_USE_SH_LIGHTMAP;
					}
					uses_lightmap = true;
				} else {
					inst->gi_offset_cache = 0xFFFFFFFF;
				}
			} else if (inst->lightmap_sh) {
				if (lightmap_captures_used < scene_state.max_lightmap_captures) {
					const Color *src_capture = inst->lightmap_sh->sh;
					LightmapCaptureData &lcd = scene_state.lightmap_captures[lightmap_captures_used];
					for (int j = 0; j < 9; j++) {
						lcd.sh[j * 4 + 0] = src_capture[j].r;