The only thing that I can think of that effect it is I have recently uninstalled Nehrim, as I also had to reinstall a few files from the DarkUI mod as that was causing problems. I could try and do trial and error hunt but I'm not sure if that would be any good and could take a long time, time saved if someone has an idea where to look. I could reinstall the whole game again but as a last resort, especially as I have quite a long list of mods. Thanks.
Edit: Found the problem. Nehrim must've overwritten and deleted more files from the DarkUI mod than I thought. Completely reinstalled all necessary files from DarkUI and has solved the issuse. Thread can be locked if need be.