A while back, I encountered an issue that I thought was triggered by OptiFine. However, upon further investigation, I discovered that the true cause of the crash was not OptiFine, rather it was Sphax PureBDcraft. I tested the result in Default, and the game ran fine, going to the third page of the inventory screen of creative mode did not trigger a game crash. However, when I turned on a different texture pack, and not one that textured Project Red at all, the game spit out the exact same crash error.

I cannot be certain of what is triggering this crash, and this is a problem, because this error has been plaguing me since January.

https://pastebin.com/euCQTR8q

https://pastebin.com/U4L79mAq

I can confirm that the error is indeed caused by Project Red, as running the game without it causes no crashes, with full Sphax PureBDcraft and modded textures loaded.

Was likely an issue with optifine, regardless, some fixes back in 1.10 would have effected this.

The second crash report has the following lines of text in it:
-- Item being rendered --
Details:
Item Type: mrtjp.core.block.ItemBlockCore@61a364a1
Item Aux: 0
Item NBT: null
Item Foil: false
Whatever block that code is identifying is most likely the culprit of this crash. What's funny is that the block crashes whenever any texture pack is enabled, and I'm talking about vanilla texture packs, ones that don't have a folder for Project Red textures.

After some further evaluations, I have found that removing OptiFine allows the blocks to render without any error, with texture packs loaded. Something tells me that since when OptiFine is not present, the Forge loading screen has an extra step to go through, then the mod is stopping something important from loading.