Fair point, but I think there maybe several reasons. One is that some may indeed have seen minor errors but their views have not be left for posterity. We know there were many who were not convinced by Muhammad's utterings and he had a long physical struggle to win Arabia over. Secondly they are minor errors and many probably never noticed (we are talking about a mostly illiterate people) or they either justified it in much the same way the later scholars did - as the mysterious ways of Allah - or were simply unconcerned. As it happens I believe they knew very well these were the words of Muhammad - albeit under divine inspiration - and it was only later generations that began to raise the Qur'an to the height of infallibility. In my opinion the reverence we have for the Qur'an today is far removed from the mentality of the people at the time. There are even several instances where companions wanted to change some things. Umar for example decided to abolish the spoils allotted to the Muslims fighters saying it must now go to the Bayt-ul-Mal. In other words directly discarding a clear injunction of the Qur'an. (When I was still a Muslim and believed that Islam needed reforming I was convinced that we needed to return to that attitude of discarding anything that was no longer applicable and often cited the examples of early companions like Umar and Abu Bakr). Thirdly the very process of repeating something over and over again in faith and devotion makes the banal seem special.
Of course Umar knew the Quran was made up. He co-authored it.
Volume 1, Book 8, Number 395:
Narrated 'Umar (bin Al-Khattab):
My Lord agreed with me in three things:
1. I said,"O Allah's Apostle, I wish we took the station of Abraham as our praying place (for some of our prayers). So came the Divine Inspiration: And take you (people) the station of Abraham as a place of prayer (for some of your prayers e.g. two Rakat of Tawaf of Ka'ba)". (2.125)
2. And as regards the (verse of) the veiling of the women, I said, 'O Allah's Apostle! I wish you ordered your wives to cover themselves from the men because good and bad ones talk to them.' So the verse of the veiling of the women was revealed.
3. Once the wives of the Prophet made a united front against the Prophet and I said to them, 'It may be if he (the Prophet) divorced you, (all) that his Lord (Allah) will give him instead of you wives better than you.' So this verse (the same as I had said) was revealed." (66.5).
Topic: Come back to Allah