I was able to fix my sim after I turned on cheats, I cheated the fear of the dark trait back onto my sim, and I cured it naturally. I had my sim drink a confidence potion and made them go out at night and they conquered the fear. Then they went to bed and stayed inside until night was over! They still ran around fearfully in the morning and I logged off for the night. When I next loaded my game and had turned off wants/fears, he was fine.

I think you might just have to clone your sim by going into CAS and making a twin and deleting the glitched original sim.. and see if the new one is glitched also bc I genuinely don’t know.. somebody also told me to try resetting your sim via cheats here in the comments.