How is Al-Farra's statement that the Qur'an contains "many things in which error is evident" to be interpreted, what is meant by this statement, and who is Al-Farra'?

No ill words could have come from Al-Farra' concerning the Holy Quran. What Al-Qurtubi said was misunderstood, and the correct understanding is that Al-Nahhas was the one who described Al-Farra's book (Ma'ani al-Quran) as erroneous. Al-Farra' is a trustworthy and distinguished scholar, one of the leading figures in the Arabic language. He authored the book "Ma'ani al-Quran" by order of Al-Ma'mun and passed away in the year 207 AH.