As for the scribes and the differences between the manuscripts they prepared, this is what has shown forth from the horizon of elucidation in answer (to your question):
O Zayn! The verses of God were revealed in such manner that no one was able verify them at the time of their revelation and those that were revealed in Iraq and Adrianople were never reviewed. The servant attending the throne [Khadim Allah] is often able to look them over, according to his capacity. Nevertheless, he has been absentminded in some places, and what the scribes copy is frequently contradictory. The people’s condition is such that they do not know if those things that contradict (their grammatical rules) were revealed by the holy court or were a result of the inattention of the scribes.
It is known that what is revealed by the Truth is the truth, in which there is no doubt. However, since Jinab-i Nazir, upon him be the glory of God, wanted to publish some of (our) books, we commanded the Greater Branch [Muhammad `Ali] and the servant in attendance [Khadim Allah] to compare them and to report those things that contradicted (the grammatical rules of) the people since most humans have not and do not understand and are unaware of the process of revelation. On account of this review, souls did not perish, although “oppressors only increase in loss.”
The Surih-yi Haykal was revealed in the Land of Mystery and later renewed in that land. This is what has been recorded before. Verily, He is the Renewer, the Knower, the Informed.
Khadim Allah (Mirza Aqa Jan), on behalf of Baha’u'llah, in response to Zayn al-Muqarribin, Baha’u'llah’s most trusted scribe. Asrar al-athar, 4:92-3. ”Jinab-i Nazir” is Hajji Mirza Abu al-Qasim Nazir, mentioned in Balyuzi’s King of Glory (396-8) and in Ali Kuli Khan’s pilgrim’s notes; the latter says Nazir worked with Muhammad `Ali against `Abdu’l-Baha (see the section on “Muhammad Ali in India”).