This happens to me too, in 18 Culpepper House in San Myshuno. I have some packs and expansions. This is a brand new save file. I haven't had mods or CC. The non-household Sims are morphing/warping through the wall and into the apartment; it has nothing to do with coming in through the door. They have the walk animation and show up in the bedroom (in the default apartment layout), spin around a few times, and sometimes leave through the door. Sometimes they can be interacted with, but sometimes they can't.
They will not leave when I use the Sim to ask them to Go Away because they are stuck and can't get out of the apartment. I tried adding them to a Group and going into the hallway together, but the non-household Sim was giving the "can't go there" error and wave. I tried both the options for resetting the Sim but they're still stuck in the apartment and can't get out.
