Describe the bug
When you place down a mirror and either create a portal with the portal gun mod or power a GLASS screen, the game has some weird graphical things happen to it and then it crashes. Both of those mods are by ohaiiChun, but I am also using a few other mods that could contribute to the issue. In the bottom left corner you can see a small square that clearly says "Shutting down internal server..." but it's being cut off because it's being rendered in a square.

Crash report
idk if VanillaFix adds more to the crash logs or not so here's both with and without it:
without VanillaFix mod (game closed itself like it normally would when crashing)--> https://pastebin.com/raw/jurbBTA3
with VanillaFix mod (game stayed open but unresponsive on a black screen)--> https://pastebin.com/raw/LGJVWxu8

To Reproduce
For portal gun mod:

1. Place down mirror
2. Place down 2 portals with portal gun so they link
3. Crash

(can reverse steps 1 and 2)

For GLASS mod:

1. Place down mirror
2. Set up GLASS rendering thing (place obsidian camera thing somewhere, place glass, place the beacon glass thing & link the beacon glass thing to the obsidian camera thing)
3. Power beacon glass thing with redstone (begins rendering what the obsidian camera thing sees onto the glass)
4. Crash

(can switch steps 1 with steps 2&3)

Screenshots
https://drive.google.com/file/d/1bn-RJtuvkMgAwiBsI-g_pGZw_8m6OYOa/view?usp=sharing

Please complete the following information:

• Minecraft Version: 1.12.2
• Mod Version: 6.3.1 (btw your website still has 6.3.0 as the latest)