One particular infuriating thing is the persistence of previous sign-ons when trying to play MCC. For example, I just concluded some solo CE campaign playing. My kids wanted to play coop campaign together. They turn their controllers on (which, by the way, were assigned to their usernames), and I turn mine off. However, my sign-in persisted as the party leader (but assigned now to a different controller). So my kid went into the roster and changed the sign-in to herself, entered her password, and returned to the menu.
At that point, there was now only one member of the party (despite two active controllers). So my other daughter turned her controller off and then back on. Kinect proceeded to log me in - even though that controller was assigned to her. So I left the room so Kinect couldn’t see me, she changed her sign-in to herself, and when she came back to the main menu, the game had switched my other daughter’s sign-in back to me. They tried re-signing in several times without me in Kinect’s view. Whatever they did resulted in either only one party member, or in my sign-in being the second party member, despite me not even being in the room anymore.
We could find no combination of this that would work, so I did a hard reboot, left the room, and they were then able to sign in as themselves.
The Kinect logon is somewhat buggy even at the main Xbox One interface, but at least if you enter your passkey it accepts that identity and doesn’t switch it back. But with the MCC - since it retains the game state when you exit back to the Xbox home menu - unless you do a hard reboot, it sometimes refuses to accept that the original player has stopped playing.
I’m going to turn off the Kinect logon entirely and force it to ask for passkeys each time, since that will actually be easier.
I wish the Xbox 360 option (simply selecting usernames from a list when the controllers were turned on) was still available.