With shaders, large tileentities break a little and black spots appear in some places

I cannot reproduce this in a test instance with BSL shaders. Send a zip file of the modpack you're testing with, along with this test world.

oh, here’s a video from malisisdoors, it was really recorded in mega, but I think it will also work without other mods.

Rather, this error is not blinking doors, but dark areas near the doors

at 3 second you can see how the dark areas near the 2nd door changed, when I turn the camera, this is exactly it

Here I tested this with hbm (https://github.com/HbmMods/Hbm-s-Nuclear-Tech-GIT), but I definitely remember that this happened with other mods. There seems to be a video from malisisDoors, but I don't know for sure if it's related to this problem.
I was only able to reproduce this with HBM + optifine.
As far as I noticed, this is most noticeable with high quality shadows.
Here are some more examples with different shadow quality: 2048 and 8192.
(Sorry for the quality, I had to compress the video due to the size)
2048:

smaller tileentities look normal, of course from a certain angle you can see a little bit, but not critical

8192:

here is what you asked for:

New World.zip

(and shaders) - BSL_v8.2.04.9d.zip

for mods, use hbm (https://github.com/HbmMods/Hbm-s-Nuclear-Tech-GIT/releases) and optifine, that's all
(even in the archive it takes up too much space for github)

Disable quad triangulation in the settings gui.

Disable quad triangulation in the settings gui.

Doesn't help, because it's an optifine shaders error, it's not caused by your mod, this is just a suggestion to fix one of the bugs with optifine shaders (happens even with just optifine and a mod that adds large tileentity)