So, took a bit longer than expected, but, with the help of Hyrule_Symbol, we managed to find what caused the error. It was because of a typo in Chabonit's mod in one of its recipes. I sent a pm to Chabonit at least, so everyone who's experiencing this issue will have to wait until he/she updates the mod.
As for this mod, there's not much that can be done. The best thing I could do is to add an error message that shows up early if a recipe is not valid, so at least the confusion won't be there should this happen again.