Describe the bug
As the title states, random crash upon singleplayer world load.

To Reproduce
Not sure how to reproduce, but figured it might still be useful to share!

Versions
RenderLib: 1.1.1
Forge: 14.23.5.2860
Minecraft: 1.12.2
Other mods (necessary to reproduce the bug): Unknown

Log File
https://mclo.gs/gQ4LG1y

This might be related to GregTechCE/GregTech#1256? and also perhaps supposed to be fixed by LoliASM (which was included) thanks to LoliKingdom/LoliASM@d7fa000, alas the crash still occurred.

Not sure if related, and still not sure if it's even caused by your mods, but I tried downgrading to Entity Culling 5.x without RenderLib and got a random ConcurrentModificationException upon opening VoxelMap.
Log: https://mclo.gs/mdVVFCE
Edit: another completely random CME crash: https://mclo.gs/cePnhBw. Again not sure if it's caused by Entity Culling or not.

This is not related to the GregTech issue.

Old EntityCulling versions are unsupported.

You can try to reproduce the issue with this version.
RenderLib-1.12.2-1.1.4-dev1.jar.zip

Got a crash with it, seems to be due to VoxelMap: https://mclo.gs/e0Ywiqv

That's a VoxelMap issue. Placing blocks is not threadsafe.

I got a couple more crashes not mentioning VoxelMap:
https://mclo.gs/80HuT6r
https://mclo.gs/ZyTR3sP
Probably still are caused due to it, I will try reaching out to the VoxelMap author although they don't seem to be active.
(I can also confirm the game does not crash in the same way when Entity Culling / RenderLib are not installed)
Edit: this appears in the log before the crash: https://mclo.gs/1Tw40yt

This is resolved by using the latest version of VoxelMapFixes.