Certainly in those times where unity was difficult, there were misunderstandings and heresies. Please be clear: for about 1000 years, if you were Christian, you believed in the Real Presence. The early writings of the saints are clear. For example, one of the earliest, St Ignatius of Antioch:
“Consider how contrary to the mind of God are the heterodox in regard to the grace of God which has come to us. They have no regard for charity, none for the widow, the orphan, the oppressed, none for the man in prison, the hungry or the thirsty. They abstain from the Eucharist and from prayer, because they do not admit that the Eucharist is the flesh of our Savior Jesus Christ, the flesh which suffered for our sins and which the Father, in His graciousness, raised from the dead.”
“Letter to the Smyrnaeans”, paragraph 6. circa 80-110 A.D.
“Come together in common, one and all without exception in charity, in one faith and in one Jesus Christ, who is of the race of David according to the flesh, the son of man, and the Son of God, so that with undivided mind you may obey the bishop and the priests, and break one Bread which is the medicine of immortality and the antidote against death, enabling us to live forever in Jesus Christ.”
-”Letter to the Ephesians”, paragraph 20, c. 80-110 A.D.
“I want the Bread of God which is the Flesh of Christ, who was the seed of David; and for drink I desire His Blood which is love that cannot be destroyed.”
-”Letter to the Romans”, paragraph 7, circa 80-110 A.D.
“Take care, then who belong to God and to Jesus Christ - they are with the bishop. And those who repent and come to the unity of the Church - they too shall be of God, and will be living according to Jesus Christ. Do not err, my brethren: if anyone follow a schismatic, he will not inherit the Kingdom of God. If any man walk about with strange doctrine, he cannot lie down with the passion. Take care, then, to use one Eucharist, so that whatever you do, you do according to God: for there is one Flesh of our Lord Jesus Christ, and one cup in the union of His Blood; one altar, as there is one bishop with the presbytery and my fellow servants, the deacons.”
-Epistle to the Philadelphians, 3:2-4:1, 110 A.D.
From what I've seen of the ECFs their only consistency is their inconsistency on the issues.
The writing of Ignatius as well as many other Catholic historians have been proven to be forgeries; lies...
The validity of authorship of Ignatius of Antioch is often false, and others questionable, but regardless, you simply do not hold the uninspired understanding of post apostolic men to determinative of doctrine, as if the Holy Spirit was negligent to show what the NT believed in providing approx. 73,000 words from Acts thru Rev, interpretive of the gospels.
And in which we see that the NT church manifestly did not teach perpetual ensured magisterial infallibility, which is unseen and unnecessary in the life of the church, nor did it have a separate class of believers distinctively called "saints" or distinctively titled "priests ," offering up "real" flesh and blood as a sacrifice for sin, which is to be literally consumed in order to obtain spiritual life. Nor is it otherwise Scripturally manifest in the life of the church as being the sacrament around which all else revolves, and the "source and summit of the Christian faith," "in which our redemption is accomplished."
Nor is the NT church manifest as looking to Peter as the first of a line of exalted infallible popes reigning over the church from Rome (which even Catholic scholarship provides testimony against), and praying to created beings in Heaven, and being formally justified by ones own sanctification/holiness, and thus enduring postmortem purifying torments in order to become good enough to enter Heaven, and saying rote prayers to obtain early release from it, and requiring clerical celibacy as the norm, among other things. No wonder Catholics rely on amorphous "oral tradition," for under the premise of magisterial infallibility all sorts of fables can be chanelled into binding doctrine, even claiming to "remember" an extraScriptural event which lacks even early historical testimony. , and was opposed by RC scholars themselves the world over as being apostlic tradition.