I had the same glitch with the main menu (not sure about CAS) a few days ago and managed to fix it. Sorry if this is long and/or confusing, I probably did some unnecessary steps lol.
When it was glitched I never clicked the resume button, I went to load game and loaded the last household I was playing and when I did it took me to the neighborhood menu. When I went to the world my sims were living in their house was there, but my sims were gone (not even in the library).
I tried what someone else suggested on another forum of repairing the game which did not fix the glitch.
I then tried launching the game without my mods just to make sure they weren’t the issue, and the glitch still happened so I put my mods back in.
I went into the game files and removed the entire saves folder, and the glitch was fixed.
I then put my original saves folder back in and deleted the new one generated. I still had the glitch after placing my original saves folder back in. So, now that I knew for sure my saves folder was the issue, I then went into my saves folder and removed only the save file with “.save” at the end (without a version #) for my most recent household (the one I last played before the glitch occurred) out of the folder and the glitch was fixed. So, it seems my save file was corrupted for that household. I then launched the game and played a different household for a few minutes so that they would appear as the last played on the menu and to ensure my sims were present in my other households – which they did. I then exited the game and placed the corrupted save file back into my saves folder. I then used the “recover save” feature on the household with the corrupted save file. I chose the most recent which when loaded it only showed the house with no family same as before. I then deleted that recovered save and then recovered the second newest recovery save and my house and family were present. Although I did lose some progress/gameplay but not very much, only a day in game.
So, in my case it seems the corrupted game file was the issue, I’m not sure if what else causes this issue. Hopefully this helps someone.