Have you ever tried to refresh your Document Sims 4 folder? Or is that what you mean by reinstalling it? I ask because I recently went round and round trying to figure out why an updated mod wasn't functioning properly. I finally got two people over at the mod creator's discord to help me. Turns out, it was a corrupted game save file.
I've since had to restart that family, from scratch. Luckily, my one Sim was in my library. I made his family using the genetics tab in CAS before. This time I played around with it, randomizing his parents and his siblings so they didn't all look so completely alike. But, the main thing is, you may need to start fresh.
I hope doing a reinstall (or refreshing your documents Sims 4 folder, if they aren't the same thing) does the trick for you. Nothing like frustration to ruin your day, eh? Best of luck to you!