Saved Sims don't appear.

[Rinbird]

I've been having this issue for some time now. Only a few of my old saved sims appear in my sim bin. (Is that what you call it?) I remake my sims a lot, and not being able to open them in CAS is really annoying. I've looked some things up but I didn't find how to fix it. Now playing is pretty boring because I have to spend hours recreating my sim and their whole household because it won't save.