It is not rational to suppose that Christians and Jews throughout the world could meet and agree on the alterations of their Holy Scripture. History shows (as well as the Qur’an in Surah 2:113) that the Jews and Christians have had major doctrinal differences between them, and they have been in disagreement regarding many religious issues.
We also read in many verses in the Qur’an (such as in Surah 3:19 and Surah 98:4) that Christians were divided into sects. So if the Scriptures had been changed to alter doctrine, at least one of the many sects that existed within Judaism or Christianity at that time would have protested. Yet there is no historical mention of any such accusation or dissension.