Here is the first part in this series, to refresh your memory.
The video runs 15 minutes. Below is my synopsis.
In 1972 a German scholar Gerd R. Puin was asked to investigate some manuscript fragments discovered in Sana'a, Yemen. What he found was fragments of the oldest Quran in existence. The text shows evidence of having been altered, with verses changed and rearranged, and missing diacritical marks permitting the existing words and verses to have a great many different meanings, not the one orthodox meaning found in the Quran today.
Another scholar, writing under the name Christoph Luxenberg, analysed the text of the Quran and discovered a great many loan words and passages that do not make sense in Arabic but make perfect sense when read in Syrio-Aramaic, the dominant language in Western Arabia and the Levant when the Quran was first written.
Together their work suggests that, far from being a single, monolithic text that has existed in its present form for over a thousand years, the Quran has, in fact, gone through revisions and significant alterations in meaning. The Quran may also have been pieced together over several generations from many different texts and may not have existed in its present form until long after Muhammad died.
We may never know the true origins of the text of the Quran (as with virtually any book from antiquity), but now people are asking questions. People are (slowly) giving the Quran the same treatment as the Bible and the Vedas and are performing critical scholarship of the text no one dare question.