Block State Culling seems to be incorrectly culling blocks behind 3D trap doors (All variants), as supplied by the resource pack. Turning the option off resolves the issue, but doesnt seem like a good long term solution, due to performance impact.

This doesnt happen for other 3D models in the resource pack, such as closed doors, ladders. etc.

Resource pack shown is Vanilla Tweaks for 1.20.6.

Similiar case - but sadly not only flapped trapdoors are being culled, but also behind glass for some reason

additionaly (Well, I'd expect it to be a feature, not a bug) x-ray mods are only showing visible side of blocks

EDIT:

This was hackfixed in 0.26.0

@FxMorin
Not sure if by hackfixed you mean something what you said in other thread, like a "sloppy" fix, but sadly it still happens in 1.21 (0.26.0)

Disabling blockstate culling resolves the issue

Before:

After:

Edit: It... fixed itself? Damn, I have no clue what I did exactly, but the issue is gone...

The issues you are getting are really weird, like with the glass

I bet they are weird... Tho I explicitly remember that I updated to Sodium 0.6 and Iris 1.8, enabled blockstate culling and... it was gone. Downgraded to Sodium 0.5 and Iris 1.7... and the issue did not reappear... Very odd XD