Intentional Changes to the New Testament - Factual and Interpretive Errors

The following quote comes from, Misquoting Jesus: The Story Behind Who Changed the Bible and Why pp. 94-95 by Bart D. Ehrman.

Sometimes scribes changed their texts because they thought the text contained a factual error. This appears to be the case at the very beginning of Mark, where the author introduces his Gospel by saying, "Just as it is written in Isaiah the prophet, 'behold I am sending a messenger before your face...Make straight the paths.'" The problem is that the beginning of the quotation is not from Isaiah at all but represents a combination of a passage from Exod. 23:20 and one from Mal. 3:1. Scribes recognised that this was a difficulty and so changed the text, making it say, "Just as is written in the prophets..." Now there is no problem with the misattribution of the quotation. But there can be little doubt concerning what Mark originally wrote: the attribution to Isaiah is found in our earliest and best manuscripts.

On occasion the "error" that a scribe attempted to correct was not factual, but interpretive. A well-known example comes in Matt. 24:36, where Jesus is predicting the end of the age and says that, "concerning that day and hour, no one knows-not the angels in heaven, nor even the Son, but only the Father." Scribes found this passage difficult: the Son of God, Jesus himself, does not know when the end will come? How could that be? Isn't he all-knowing? To resolve the problem, some scribes simply modified the text by taking out the words "nor even the Son." Now the angels may be ignorant, but the Son of God isn't.