When the killSessions command is executed, it will attempt to kill cursors associated with the sessions being killed. As part of this, it will build a list of cursors owned by a session and then kill each cursor in the list. It is possible that in between list fetch and kill that a given cursor is killed by an external operation. When this occurs, a CursorNotFound error will be returned on attempt to kill. While we will continue to kill the remainder of the list, this error will be returned to the user. This is misleading because the end result is the same with all session resources being freed.