originally downloaded some resourcepacks for a mod called Immersive Railroading, along with a mod known as buildcraft. This started happening with start crash screen and mods tab, and a few other things.

Start crash error: https://gyazo.com/76cf66171f55765d738fa8714c24095c

menu error (fml.menu.mods shouldn't be there): https://gyazo.com/3f187de413aed7f28f2ca439b08d18d7

Edit: New thing popped up

I'd like to say this is because of us, but the unformatted lang isuse hasn't been an issue since the first versions of the mod. This has to be something for either Immersive Railroading or Buildcraft as this doesn't happen normally.