Specifically gave one of my legacies kids the unstable trait and it's interesting to say the least. Seen her talk to herself in the mirror but that may because she also has the insane trait...
Generally, or at least in my case, my sim will be out of sorts, i'll let her use the paper bag and send her to the hospital if it's too far advanced for the bag to help.
Been having fun letting the traits reset, but if i want to keep one on her i like, i'll take her to the hospital for the cure.
Although i've never had the problem of not being able to direct her though even WHEN out of sorts. Always played like a normal sim so far. You do the Reset sim? Maybe that will help. Sounds like a glitch to me.
Still playiing around with it so if anything different pops up i'll let you know.