It happens to the sims that are made from play with genetics, so I guess mixed everything. I think I've found the source of it.
My brother downloaded LC on his computer. His files were all original; no mods/cc, no modified graphic rules, no camera mods. Right after downloading the game we started checking this bug and it happened in his game too. So it seems like it's in-game problem, maybe with LC but idk as my friend has UC. I don't know if there's a way to fix this, so I'm just going to avoid undoing things in cas.
The only thing that didn't happen was a borked camera that got out of cas, so I think you were right and it's an issue with GunMod's camera mod.