it is likely this is an official game bug

Hi JOyyyySOFIALL​ 

you seem to have an issue with a milestone that was on a cc that you removed from the game.

Try this mod: https://www.patreon.com/posts/mod-milestone-81237568  (File 2: CC/Mod Object Fix).

It's a script mod so make sure to turn those on. You can remove the mod after fixing the issue.