Alright, I figured it out. It was PMMO and Curios API that are conflicting just a bit. I found this out after I removed PMMO, which apparently fixed the bug. I thought "hey, that's kinda weird, cause it never caused any problems before". So I guessed that it must be a mod conflict. Then I went through the PMMO discord, and yup, it was curios. Thing is, Curios is kinda needed for like half of the item mods I installed, so I'm at a dead end here. At least I know to look out for the next release for both.