[Bug] Entities turn completely dark

[Elcamian]

Description of Issue

Ever since 1.21.3, and still on the latest 1.21.4 optifine preview, for some reason entities constantly flash between being normal or completely dark (like the chicken or the item frames on the screenshots), I have no idea why this happens, but I know its an optifine bug because this doesn't happen if I play on vanilla, I tried turning CEM off but that doesn't do anything.

Steps to Reproduce

Booting up the game with optifine and joining any world or server, it happens on both singleplayer and multiplayer.

OptiFine Version

1.21.4_HD_U_J3_pre5

Installation Method

Through the official website, downloaded the installer and executed it.

Prior Testing

It doesn't happen in vanilla, only with optifine enabled

Additional Information

This affects only entities like mobs, paitings or item frames, not block entities like chests

[Elcamian]

More screenshots of this happening plus some new findings.
Mobs that are holding/ wearing tools and armor, straight up go invisible, except the objects they are holding, I also found out that chests are indeed affected as well, I left an f3 screenshots if its of any help.

[Elcamian]

Did more testing and it seems like turning off mipmap somewhat reduces the flashes from happening, but they do still happen, just more rarely, I also found out that on third person I also go invisible, so its just all entities, and block entities

[Xyral1]

if custom sky is enabled, it goes completely invisible

[Elcamian]

Bug still happens on pre6, gonna keep updating this as more previews come out

[Elcamian]

It just keeps getting worse and worse

[Elcamian]

I'm honestly losing my mind, somehow it got worse on the latest preview, and now when I press f1 entities blink constanly and the sky gets weird when I look in certain directions

[sp614x]

Resource pack, error log?
Disabling Render Regions, Fast Render and Dynamic Lights?

[Elcamian]

I only have in use a resource pack that removes 1.16+ music, first screenshot shows all of the resource packs I have, I tried only disabling render regions and fast render, that somehow fixed it for the most part, except on one scenario, whenever I press f1 and remove the gui, it happens again, entities start to flicker

[Elcamian]

Also I forgot to add that I can't provide any error logs because this literally just happens while playing normally

[sp614x]

The error log is in logs/latest.log, it has a lot of information.

[Elcamian]

I would love to check that, but now my game doesn't even open on pre9, it has been like this for 2 hours

[Elcamian]

This is the log for this
latest.log

[Elcamian]

Just checked pre8 and that one works, f1 bug is still present but it at least opens up, here's the log for it btw
latest.log

[Elcamian]

My game now opens on pre11, but the f1 bug still happens, gonna provide screenshots and logs as always
latest.log