Votes made invalid or informal BECAUSE of the AEC?

Listening to the radio this morning one scrutineer said that something like 30% of votes declared informal at her booth  were because the AEC official issuing the ballot paper to the voter had not initialled it in the top right hand corner. Does this error by the AEC make a vote informal? And if so is there any redress because they wouldn’t know who unknowingly lodged the invaded/informal vote.