Failed to save error code 403

Hi, 

My game is currently failing to save, and when I try to play one of my saved households, the game keeps going back to the manage world screen. When I resume the game from the homescreen, it also shows a distorted corner UI... 

I play with cc and have spent the last day testing which ones were causing the black main screen. I finally fixed that issue, and now I have this problem. I have tried to do a save as with the mods folder, and it won't work. I have managed to save as but only once the mods folder is removed.

I have installed TM better exceptions, and it hasn't flagged anything (apparently). I don't have WW installed, and I have downloaded all of the newest versions for MCC. 

I am not sure what to do, and I am getting quite frustrated, constantly having to troubleshoot mods and cc, but I don't want to play without it lol...

Is there a solution? Or a way to quickly check what is causing the problem?