A valid question exists: What might ASX’s motive be for ISX’s continued suspension?, page-41

to give isx the benefit of the doubt they have been audited by Grant Thornton for a number of years. A financial audit is not fool proof, and I think a mid tier firm like Grant thornton likely won't have as high quality as a big4 hence this issue may have been missed by GT, particularly when ISX was a micro cap back when the performance shares were granted.

there is constant news in Australia and internationally about poor audit quality so it wouldn't surprise me if there is a historical issue with revenue recognition, particularly when the margin was only a few thousand dollars that they met that last hurdle.