I'm familiar with the command. I've used it to switch to non-active sims and to successfully interact with the borked one. However, I haven't tried making a new family sim to snatch the borked one. If anything, it'll prove whether or not that sim is singularly borked.
EDIT: Well, after trying this with two separate new characters, I've found, to my chagrin, that the original character is indeed ruined. I'll just make a new one and see if the issue re-appears. If it does, I'll try to find out what exactly causes the error and try to duplicate it so that the AM team can correct it (assuming that there is a conflict with AM).
You've all been very helpful and succinct (pressed the "Thanks" button, laughed for a few minutes). I can't understand why others have such difficulty interacting with MATY users.