A reported critical case concerns Ghiyāth ibn Ibrāhīm, who is said to have added “aw janāḥ” (“or a wing”) to the wording of a report about permitted racing contests before the caliph al-Mahdī, apparently to appeal to the caliph's interest in pigeons. The added phrase is not a reliably preserved part of the report.
The issue is not an ordinary difference in pronunciation: it is an interested alteration of the text. The preserved report must be separated from the alleged invention attached to it.
The incident illustrates the need to investigate suspiciously convenient additions while also avoiding a presumption that every statement aligned with someone's preference is fabricated.