Michael Kruger wrote a nice piece comparing the conspiracy theory that Jesus was married to Mary Magdalene to the old whack-a-mole game. Remember that game? Mostly for younger kids, we played it at the arcades. This mechanical device that looks (sometimes) like a mole pops up in a hole and, as fast as you can, you hit him with your hammer. Successful or not, that one goes down and another one pops up somewhere else. No matter how good you are at it -- no matter how quick, unerring, accurate -- they just keep coming. Kruger says that this conspiracy theory is like that. You find this claim being made and you carefully, biblically, reasonably, factually give it the smackdown, only to see it popping up over there again.
I'd argue that he was right, except that it's not just the "Jesus was married to Mary" story. It's most biblical doctrines. Paul, for instance, carefully shot down the "saved by works" dogma of his (and our) day, only to have Peter kissing up to the judaizers and have to shoot him down (Gal 2:11-21). In his epistles he had to take down that "saved by works" thing repeatedly. That mole has been beaten down over and over and still comes up today.
Consider the Scriptures themselves. The early church had what they considered to be God's Word. It was a given. They all knew what it was. Then some upstarts came along and started parsing out their own "Scriptures". "This, not that, a little of my own." So they got together at the Council of Laodicea (AD 363) and clarified what was already known -- that the 39 books of the Old Testament and the 27 books of the New Testament were "God's Word". Settled. But not. They did it again in the Council of Hippo (AD 393). And again at the Council of Carthage (AD 397). And even today we're hearing about "the lost books of the Bible" as if such a thing exists. Whack that mole and another appears. Indeed, since the origin of Man "what God said" has been debated endlessly long after having been settled. Whack!
Take the Trinity as an example. The Arian Heresy said that Jesus was a product of God, not God Himself. So Constantine called a meeting (called the Council of Nicaea) in AD 325 to settle the matter. (Constantine would have preferred them to settle it in Arius's favor.) They decided that Arius was wrong and the doctrine of the Trinity was settled ... right? You'd think so, but even though Scripture is replete with it, multiple councils since and the rest of the Church have had to over and over whack that mole while more spring forth right around the corner to today in such groups as the Jehovah's Witnesses, some Pentecostal groups, and the Mormons to name a few.
We see this a lot. Every major biblical doctrine is picked up, confirmed, decided, argued, denied, and the circle starts again. Why is that? Why is it, for instance, that if Scripture is as clear as the Church has long claimed that the argument is still made that the Scriptures aren't as clear as the Church claims and we can't really know for sure? Is it because they're right? Are the moles correct?
No, of course not. Whack!
The Bible promises that this will be the case. The New Testament is full of warnings of false teachers. Paul, Peter, and especially Jesus have multiple warnings of false christs and false teachers and false prophets. Jesus says you can tell them by their fruits (Matt 7:15-16), which must disturb those who warn of examining others and their lives. Of these false teachers John says, "They went out from us, but they were not of us; for if they had been of us, they would have continued with us. But they went out, that it might become plain that they all are not of us." (1 John 2:19) Paul warns that it is partly the people who are to blame for this problem, not being willing to endure sound teaching, "but having itching ears they will accumulate for themselves teachers to suit their own passions." (2 Tim 4:3) Their "new and improved" gospel, Paul warns, is not a gospel (Gal 1:6-7) and those who teach such things are accursed (Gal 1:8-9), to be avoided (Titus 3:10-11), a product of the last days (2 Tim 3:1-9).
So, yes, it is a bit like a doctrinal whack-a-mole. You find a heresy, you "contend for the faith that was once for all delivered to the saints" (Jude 1:3), you pray and leave it in God's hands, and you move on, knowing it isn't over and that pesky heretical mole will pop up again sooner or later despite the sound beating it has taken over and over from God's Word and His faithful followers. And we pray with John, "Come, Lord Jesus!" (Rev 22:20)