### 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
sdcache->shader = p_material->shader_data;
	sdcache->material = p_material;
	sdcache->material_uniform_set = p_material->uniform_set;
	sdcache->surface = mesh_storage->mesh_get_surface(p_mesh, p_surface);
	sdcache->primitive = mesh_storage->mesh_surface_get_primitive(sdcache->surface);
	sdcache->surface_index = p_surface;
	if (ginstance->data->dirty_dependencies) {
		RSG::utilities->base_update_dependency(p_mesh, &ginstance->data->dependency_tracker);
	}
	
	sdcache->shader_shadow = material_shadow->shader_data;
	sdcache->material_uniform_set_shadow = material_shadow->uniform_set;
	sdcache->surface_shadow = surface_shadow ? surface_shadow : sdcache->surface;
	sdcache->owner = ginstance;
	sdcache->next = ginstance->surface_caches;
	ginstance->surface_caches = sdcache;
	
	sdcache->sort.sort_key1 = 0;
	sdcache->sort.sort_key2 = 0;
	sdcache->sort.surface_index = p_surface;
	sdcache->sort.material_id_low = p_material_id & 0xFFFF;
	sdcache->sort.material_id_hi = p_material_id >> 16;
	sdcache->sort.shader_id = p_shader_id;
	sdcache->sort.geometry_id = p_mesh.get_local_index(); 
	sdcache->sort.uses_forward_gi = ginstance->can_sdfgi;
	sdcache->sort.priority = p_material->priority;
	sdcache->sort.uses_projector = ginstance->using_projectors;
	sdcache->sort.uses_softshadow = ginstance->using_softshadows;
}
void RenderForwardClustered::_geometry_instance_add_surface_with_material_chain(GeometryInstanceForwardClustered *ginstance, uint32_t p_surface, SceneShaderForwardClustered::MaterialData *p_material, RID p_mat_src, RID p_mesh) {