Dasies45 I meant this error in particular:
[CURRENT ISSUE] Sims 4 already running | EA Forums - 11818313
Some of the workarounds there are useful in any case, but it's not exactly the same thing as what you're seeing. Still, you can try those suggestions.
Whether your cc is outdated or not, it's critical to test without it, and without your mods. You don't need to save your progress. And if the issue with the hairs is only happening to cc hairs, then the cc is the issue, whether it's outdated or just not built for the graphics settings you're using.