Quranic Imperfection - Part 1

Muslim generally believe that the Quran is perfect meaning it is complete and error free. However, a close examination of the evidence suggests that the Quran is incomplete and therefore imperfect.

1. Part of Quranic revelation was eaten by a goat

Sunan Ibn Majah, Book of Nikah, Hadith # 1934)
Narrated Aisha 'The verse of stoning and of suckling an adult ten times were revealed, and they were (written) on a paper and kept
under my bed. When the Messenger of Allah (SAWW.) expired and we were preoccupied with his death, a goat entered and ate away the paper.'

Sahih Bukhari 8.817, regarding the revelation of the stoning verse for adultery, records:

…In the meantime, Umar sat on the pulpit and when the callmakers for the prayer had finished their call, Umar stood up, and having glorified and praised Allah as He deserved, he said, "Now then, I am going to tell you something which (Allah) has written for me to say. I do not know; perhaps it portends my death, so whoever understands and remembers it, must narrate it to the others wherever his mount takes him, but if somebody is afraid that he does not understand it, then it is unlawful for him to tell lies about me. Allah sent Muhammad with the Truth and revealed the Holy Book to him, and among what Allah revealed, was the Verse of the Rajam the stoning of married person (male & female)… I am afraid that after a long time has passed, somebody will say, 'By Allah, we do not find the Verse of the Rajam in Allah's Book,' and thus they will go astray by leaving an obligation which Allah has revealed. And the punishment of the Rajam is to be inflicted to any married person (male & female), who commits illegal sexual intercourse, if the required evidence is available or there is conception or confession. And then we used to recite among the Verses in Allah's Book: 'O people! Do not claim to be the offspring of other than your fathers, as it is disbelief (unthankfulness) on your part that you claim to be the offspring of other than your real father'…

Sahih Muslim 17:4194 also talks about revelation of the verse for stoning adulterers that was lost:

Abdullah b. Abbas reported that Umar b. Khattab sat on the pulpit of Allah's Messenger (may peace be upon him) and said: Verily Allah sent Muhammad (may peace be upon him) with truth and He sent down the Book upon him, and the verse of stoning was included in what was sent down to him. We recited it, retained it in our memory and understood it. Allah's Messenger (may peace be upon him) awarded the punishment of stoning to death (to the married adulterer and adulteress) and, after him, we also awarded the punishment of stoning, I am afraid that with the lapse of time, the people (may forget it) and may say: We do not find the punishment of stoning in the Book of Allah, and thus go astray by abandoning this duty prescribed by Allah. Stoning is a duty laid down in Allah's Book for married men and women who commit adultery when proof is established, or it there is pregnancy, or a confession.

So Quran does not contain part of the revelation given to it because it was eaten by a goat. This makes the Quran incomplete and imperfect. 

2. Part of the revelation forgotten by reciters

“We used to recite a surah which resembled in length and severity to (Surah) Bara'at. I have, however, forgotten it with the exception of this which I remember out of it: "If there were two valleys full of riches, for the son of Adam, he would long for a third valley and nothing would fill the stomach of the son of Adam but dust".Sahih Muslim, Vol. 2, p.501)

Here we see the evidence for a whole missing chapter.
These evidences from Islamic tradition prove the fact that Quran is incomplete and imperfect.