I am on latest KMC CORE and its all ok with that. Something wrong with your mods\profile. You unpacked mod with 7zip? I can only suggest to reinstall Core by downloading again archive, deleted old one from mods folder and then unpack it, dont forget to delete cache folder again and delete it only with closed launcher and server!!!. 1% chance that you hdd or ssd broken, but in other cases most recent problem is Unzipping AKI MODS archives with Winrar or something old and useless)
... It was WinRAR...