### 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
RID li = p_render_data->render_shadows[i].light;
			RID base = light_storage->light_instance_get_base_light(li);
			if (light_storage->light_get_type(base) == RS::LIGHT_DIRECTIONAL) {
				p_render_data->directional_shadows.push_back(i);
			} else if (light_storage->light_get_type(base) == RS::LIGHT_OMNI && light_storage->light_omni_get_shadow_mode(base) == RS::LIGHT_OMNI_SHADOW_CUBE) {
				p_render_data->cube_shadows.push_back(i);
			} else {
				p_render_data->shadows.push_back(i);
			}
		}
		
		for (const int &index : p_render_data->cube_shadows) {
			_render_shadow_pass(p_render_data->render_shadows[index].light, p_render_data->shadow_atlas, p_render_data->render_shadows[index].pass, p_render_data->render_shadows[index].instances, camera_plane, lod_distance_multiplier, p_render_data->scene_data->screen_mesh_lod_threshold, true, true, true, p_render_data->render_info);
		}
		if (p_render_data->directional_shadows.size()) {
			
			light_storage->update_directional_shadow_atlas();
			RD::get_singleton()->draw_list_begin(light_storage->direction_shadow_get_fb(), RD::INITIAL_ACTION_DROP, RD::FINAL_ACTION_DISCARD, RD::INITIAL_ACTION_CLEAR, RD::FINAL_ACTION_CONTINUE);
			RD::get_singleton()->draw_list_end();
		}
	}
	
	bool render_shadows = p_render_data->directional_shadows.size() || p_render_data->shadows.size();
	bool render_gi = rb.is_valid() && p_use_gi;
	if (render_shadows && render_gi) {
		RENDER_TIMESTAMP("Render GI + Render Shadows (Parallel)");
	} else if (render_shadows) {
		RENDER_TIMESTAMP("Render Shadows");
	} else if (render_gi) {
		RENDER_TIMESTAMP("Render GI");