Great post and thankyou for quoting the Holy Quran.
The Baha'i interpretation of this verse would find reference to the dual nature of the Holy Prophets, their human aspect which is subject to human frailties (they still have needs, feel pain, emotions etc etc) and the DIVINE aspect which is of God and is somehow connected to the Primal Will or Logos.
When the Prophet speaks, He acts as a form of channel for the Word of God to flow and this verse from the Quran you quote, is simply saying that the Prophet as a human being "could" speak errors, but this "error" is not enabled to become reality when He speaks as a Prophet, rendering the Words spoken by the Prophet as infallible. The Word of God is infallible at the time of Revelation. We must not forget that there is a difference between the Word of God spoken by the Divine Prophet and the word of man spoken by the human being called Muhammad. There is a clear and distinct difference and the Quran is a testament to that.
Of course, due to the reliability of Baha'i historical records we now have insights into the nature of the Prophet that has never been recorded in religious history. The proximity of the lives of the Bab and Baha'u'llah to modern times are a priceless gift for humanity.
