CAS Corrupted, sims copying names and traits over

Product: The Sims 4
Platform:PC
Which language are you playing the game in? English
How often does the bug occur? Every time (100%)
What is your current game version number? 1.108.335.1020
What expansions, game packs, and stuff packs do you have installed? Lovestruck, Werewolves, Island Living, Get Famous, My First Pet Stuff, Dine Out, Cats and Dogs, Vampires, City Living, Get Together, Spa Day, Get To Work
Steps: How can we find the bug ourselves? Going into CAS, adding a second sim to the household
What happens when the bug occurs? Whenever I add a second sim to a household, it will copy the names and traits from the first sim to the next, as well as any other sims I add. In CAS, if I add a sim from my library and replace the household, the name will show up as "_____", and the pronouns will show up as "(/)". I thought it was as minor issue at first, but it happened to almost every sim I tried to recreate.
What do you expect to see? New sims do not appear as "____" in cas, my first sims name and traits to not carry over to the rest of the household, cas overall working normally.
Have you installed any customization with the game, e.g. Custom Content or Mods? Yes
Did this issue appear after a specific patch or change you made to your system? Neutral/Not Sure 

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I came across this with one of my households with two male sims. When I went to hover over the second sim and noticed that he had the same name as the other. I went into CAS to edit them (without cas.fulleditmode), and my first sim's name and traits were copied over to my other sim. I tried to edit the second sim's name, but it stayed the same—but weirdly enough, when I went back into the game, it said his named changed to the name I tried to fix it with.

I didn't touch it after that, but after the most recent update, I went back in game and noticed that his sim was completely gone, as well as another sim in a home with one cat. I tried to add him back to the household via my library, but the glitch occurred again, so I just moved him into a separate household and away from the sim that was copying the name over. He lives in a solo home now. That didn't even seem to work, because now whenever I modify him in cas, the loading screen goes on forever and never actually sends me to cas, and the only way for me to get out of it is by force-quitting the game.

I have a feeling it's because the other day I went in used cas.fulleditmode to replace a sim's trait that I did not like (it was the 'Loner' trait, and I replaced it with a modded trait). I have read that people say it's due to an additional trait, which I don't recall seeing, ever. It makes my game almost unplayable, which is really disappointing, because I've spent hundreds of hours on my current world, and I can't seem to find a single fix. All of the forums I've looked through have been dated a year or so back, and I'm way past the supposed update that people said fixed it, so I'm hopeless. If this is something un-fixable, just let me know, because I'm pretty close to just quitting the game for good, lol.