From Irish Time's article, 12,900 citizenship forms ruled invalid.
The main reasons are: a failure to provide certified copies of documents (39 per cent); statutory declarations not completed correctly (25 per cent); affidavits needed (15 per cent); supporting documentation needed (10 per cent); name discrepancies between form and certificates of birth and marriage (5 per cent); and forms being incomplete or altered with correction fluid.
(Via Irish Times online)