Minecraft Version: 1.12.2
Optifine: Yes, Version: 1.12.2 HD U D3

I just discovered this issue today when I was designing my bunker type base.
I had used a reinforced door at the very front of my base then a bunch of security doors that line the hallway and other rooms. I noticed that whenever I looked through the transparent part of a door every other door would just vanish like some weird vampire doors looking through a mirror. I have two/three examples of these:

Example 1: Door closed: https://imgur.com/Ry9hhC9 Door opened: https://imgur.com/CZUaSo7
Example 2: Different Door facing the reinforced door: https://imgur.com/HyaW7ly
(It seems that the corners of the reinforced door stay rendered when looking through transparent parts of doors)

I do have optifine installed and I am unsure if this is one of those incompatibility issues. If you need anything else in terms of debug stuff please let me know! Thanks!