### Godot version

v4.0.beta12.official [3c9bf4bc2]

### System information

Windows 10, AMD Radeon RX 480 4 GB RAM, 16 gb ram, Intel CPU 4 cores.

### Issue description


When switching to mobile render from forward + The alpha texture on the tree mesh starts to flicker.
Made a video: https://www.youtube.com/watch?v=WdGVi1hdRHo



### Steps to reproduce

Switching to mobile render from forward +

### Minimal reproduction project

Uploaded the project in google link: https://drive.google.com/file/d/1efEV914CWkyWoGzkv3RBMnw9t-4BVTeQ/view?usp=sharing
(only deleted the .godot - i guess its not needed.)
Viewport *viewport = viewport_owner.get_or_null(p_viewport);
	ERR_FAIL_COND(!viewport);
	if (viewport->use_occlusion_culling == p_use_occlusion_culling) {
		return;
	}
	viewport->use_occlusion_culling = p_use_occlusion_culling;
	if (viewport->use_occlusion_culling) {
		RendererSceneOcclusionCull::get_singleton()->add_buffer(p_viewport);
		RendererSceneOcclusionCull::get_singleton()->buffer_set_scenario(p_viewport, viewport->scenario);
	} else {
		RendererSceneOcclusionCull::get_singleton()->remove_buffer(p_viewport);
	}
	viewport->occlusion_buffer_dirty = true;
}
void RendererViewport::viewport_set_occlusion_rays_per_thread(int p_rays_per_thread) {
	if (occlusion_rays_per_thread == p_rays_per_thread) {
		return;
	}
	occlusion_rays_per_thread = p_rays_per_thread;
	for (int i = 0; i < active_viewports.size(); i++) {
		active_viewports[i]->occlusion_buffer_dirty = true;
	}
}
void RendererViewport::viewport_set_occlusion_culling_build_quality(RS::ViewportOcclusionCullingBuildQuality p_quality) {