Have you ever tried it with zero mods? I've never seen either of those objects fail to occlude properly and I'm running on an APU, my conjecture is you're running low on resources as it is, then adding a bunch of mods on top of it.
And if you're on day 5 after realizing you still had your world calling old out of date, non-vanilla zombies from mods, you def haven't started a new one and likely have bloated issues.
Try removing your whole mod folder, make a brand new world and try again. Mess with texture settings, see if this still happens. Then add your mods one by one.