The Masoretic version is indeed accepted as authoritative, but since the Tanakh is such a remarkably complex work, including tens of thousands of details  - letters, vowels, cantillation marks, etc. - in many instances the general acceptance of an authoritative version was not sufficient for it to be implemented with perfect accuracy throughout the Jewish Diaspora.

Courtesy of the Virtual Beit Midrash, Yeshivat Har Etzion