I remember looking into the prospects of challenging a meeting some time ago and came across the case below in the District court.
Trigas v The Owners – Strata Plan No. 10579 [2019] NSW from (27)
https://www.caselaw.nsw.gov.au/decision/5d747241e4b0ab0bf6071cb8
at 29. The question here is whether there can be discerned a legislative purpose to invalidate any act that fails to comply with the conditions imposed on meetings of the executive committee…
So it would seem to depend on the exact circumstances but in this case the lack of proceedures (ie no meeting notices) did not have any effect on the decisions made by the EC!
There is another case I have read at NCAT where a meeting was invalidated, but a subsequent meeting took place and corrected the problem, so whilst the lot owner won the case and had the meeting declared invalid, in the end it didnt matter anyway.
Disclaimer: This is not legal advice.