The active word is “may” – there appears to be no compulsion to do so.
However, any owner could raise an action at Fair Trading/NCAT to seek orders that the committee fills the vacancy under Section 232 (2) “Failure to exercise a function”.
Perhaps a vague threat that this option might be open to owners, including existing committee members and candidates, might focus the committee’s thoughts on a compromise. Whether it would fly or not is another matter, but concerns about the mediation and Tribunal process might dislodge one member from an entrenched postion.