I was incorrect when I stated previously that “If there are no signatures and no completion of the Attestation then the document with the seal is unlikely to be legal.”
It appears from the following extract from a 2009 article that: “Affixing the common seal of the Owners Corporation (“OC”) to any document turns that paper into evidence – evidence to the world the OC approves of and will be bound by whatever appears above the seal.”
https://www.ocn.org.au/sites/default/files/090805%20The%20Common%20Seal.pdf
If there has been a genuine mistake made and the Common Seal has been affixed to a document without the proper authorisation by the OC then this matter should be corrected ASAP.
Incorrect and/or fraudulent use of the Common Seal breaches both the SSMA 2015, and the Corporations Act 2001. Penalties may apply.
Perhaps you should phone the Office of Fair Trading and explain your dilemma and ask for their advice.
In my opinion, approving the document would require a Resolution at a General meeting with the vote on the Resolution (either Ordinary or Special) to be according to the original subject matter of the document.
In the interests of transparency (and in case this ever needs to be brought to the attention of the Tribunal), Explanatory material may need to be added to the resolution that explains the mistake.
From reading many Tribunal decisions over the years, the Tribunal recognises that mistakes can and do happen from time to time, however the Tribunal is unlikely to compound the mistake in the manner that you suggest.
The remainder is a bit too vague to comment on.