CSG shapes get culled (double?)

### Tested versions

I suspect it's a doubles problem but investigating. I'm posting it here to keep track of the investigation. I can't tell if it's our fork or master.

- Not Reproducible in https://github.com/godotengine/godot/commit/c7f56d327d265fa7b2541fe7c5e6cc1730661749
- https://github.com/V-Sekai/godot/commit/45f07c4be4ab6007233a2ffb73d05747f018d834 (doubles)
- Not reproducible in 4.2

### System information

Mac Mini, Apple Silicon, M2 Pro

### Issue description

CSG shapes get culled. It's somehow related to occlusion.

https://www.youtube.com/watch?v=gQND11TyH-4

### Steps to reproduce

1. open res://game/sandbox.tscn in the editor
2. move around
3. see the csg vehicles disappear

### Minimal reproduction project (MRP)

[godot-crappy-contraptions-main.zip](https://github.com/godotengine/godot/files/15084447/godot-crappy-contraptions-main.zip)

Open the attached godot-crappy-contraptions-main.zip and reproduce the disappearance from res://game/sandbox.tscn while moving around in the editor. Compare the listed fork and master commits, including the doubles build, and check the reported relationship to occlusion. Done means identifying the conditions that cull the CSG vehicles and confirming whether the behavior is present in the relevant versions.

Written by the indexing model from the issue text.