Versions

Betweenlands version:

TheBetweenlands-3.7.3-universal.jar

Forge version:

forge-1.12.2-14.23.5.2855.jar

Singleplayer or Multiplayer:

Singleplayer

Installed mods:

OptiFine_1.12.2_HD_U_G5.jar, TheBetweenlands-3.7.3-universal.jar
Nothing else

Link to full crash log

latest.log
debug.log
crash-2021-06-02_20.10.22-client.txt
This last file is a forced crash log, since the game just soft-crashes otherwise, generating no logs.

Description of the problem

How to reproduce:

1. Have B:use_shader=true (default) in the mod settings
2. Enable any shaderpack with dimension support. Good example: Complementary (very glitch-free shader, supports mods). Bad example: BSL (is disabled on the Betweenlands, won't trigger the bug (but won't work either)).
3. Go to the Betweenlands by using the swamp thing on a sapling and entering the portal
4. On my setup, the game will visually freeze 100% of the times. The game engine (including sounds) will keep playing and running, but the graphics will be stuck, meaning you can't see anything until you reopen the game (render engine crash). Will crash again once you join the world again.
5. Not even blindly leaving the world and returning to the main menu will un-crash the game.

Expected result:

Game renderer should not crash on the Betweenlands with shaders enabled.

Actual result:

Game renderer crashes on the Betweenlands with shaders enabled.

Confirming the continued existence of this issue. In my case, I was using Sildur's Enhanced Default Fast Version 1.13 with the latest stable build of Optifine for 1.12.2, and attempting to go through the portal into the Betweenlands, or loading into a saved world with my character already in the Betweenlands, with Sildur's shaders enabled leads to my client completely freezing up and requiring me to go to task manager to end the process.

Tested Optifine F5. It gives me a full crash on startup instead of a render crash upon render
crash-2021-06-13_04.18.55-client.txt

G5 works better, but still crashes when we try to run betweenlands and optifine shaders at the same time. It's more or less a known issue but the crash is really annoying