Byrna Beams Remain If Byrna Item Set to False
I'm not sure if this was ever addressed, but if you have the Cane of Byrna active, and something sets the Cane of Byrna item to false, the Byrna orbits remain, and the item remains active, until the player leaves the screen.
Likewise, the Byrna orbits remain if it is activated, but not in one of the two item slots (i.e. if the user shifts items). That should be a quest rule (Byrna can remain active even if not a current/selected item), that the user should be able to disable.