As some of you know I'm Jewish, but I've been working as a Biblical philologist for some years now (and as such I hold no belief in the New Testament outside my academic interest). The information here in this thread is a little vague because you have not defined your parameters.
For instance, the Catholic Church holds that the Bible was "fixed" in its official state as an inspired document once the canonization process came to an informal end in the 4th century when Eusebius wrote his canon table and it was repeated as part of Athanasius' Easter message. Thus the documents in the final state only are inspired, with retractions and interpolations part of the inspiration process.
Mainstream Protestants hold that the canon was in need of readjustment that began with the Reformation in the 1500s and ended in the late 1800s with the formation of Protestant Bible societies that formally removed the Deuterocanonicals. That settles the canon for them.
Fundamentalist Protestants hold that the official canonization is irrelevant. Some believe that certain retractions and interpolations should be removed and hold that the works were inspired mainly in the original form. Because critical scholarship makes it impossible to reach such a conclusion, this form of analysis is rejected. This leads to such theories as Matthew originally being written basically as we have it today instead of developing from various sources until reaching the current state.
Those Christians that embrace critical scholarship do not believe in the type of Biblical inerrancy promoted by Fundamentalists, in which each and every word is true. Therefore "errors" of various types do not take away from the underlying message. But the literal conservative view demands that each word be essential because of a belief that the NT texts are historical reports. Therefore Fundamentalists explain away errors through complex exegesis in order to hold their theological paradigm in place.
Therefore you need to define what you first view the New Testament as, a book of religious truth or of historical fact. You also need to define whether you are defining error by means of Fundamentalist exegesis or that as embraced by critical scholarship. adopting the conservative definition will require adopting a religious take, but taking the liberal side requires following a methodology.
What is viewed as an error to some may have little significance to others who see variables in the text as insignificant.
Being on the side of critical academia, there are significant errors in claims to being eyewitness reports. Matthew for instance belies being an eyewitness or the apostle Levi (as traditionally believed) in his description of the Triumphal entry. He has Jesus ride on two animals, a donkey and its colt, in fulfillment of Jewish prophecy whereas everyone else has one donkey. The reason is that Matthew mistakenly reads the prophecy of Zechariah 9.9 as prose instead of poetry. The poetry reading is the accepted Jewish understanding, that a "donkey, even a colt" is not mentioning two animals but defining the one animal he rides. Uncharacteristic of an eyewitness, Matthew invents a second animal to lead along with the first because of desperately wanting Jesus to "fulfill" Jewish prophecy due to his misreading of Zechariah as if it was literally speaking of two beasts. All other Gospel accounts make no note of TWO animals.
There are similar "errors," but whether or not they have any effect on the reader depends on their particular approach. This one changes nothing for the one who believes in critical scholarship because this approach uses such data to prove that St. Matthew was not the literal author or an eyewitness to the events reported by Mark and Luke and agreed upon in John, which is actually a review of the canonical reports (often ignorant of Matthew's existence). For the Fundamentalist it produces a crisis that requires an avalanche of explanation and doctrine.
