I decided to move in a bunch of Maxis Sims from the gallery and noticed immediately that I cannot transfer Sims to a new household now.
Edit By Crinrict: Adjusted Title to better reflect ...
Ideas
I've been dealing with this for like, two weeks. What I do to fix this, and it's a bit time consuming, is take a homeless NPC and move them into the place I want to move my sim to. I then move my sim in with the NPC and delete the NPC in CAS.