There were three witnesses at the Transfiguration, and Apostle John not even making mention of this amazing experience throws much doubt upon his sincerity, I think.
Yes... Peter, James and John.
Now that you mention it, Peter didn't mention it in his epistles, James doesn't mention it and John didn't mention it.
Perhaps you are putting more emphasis in what wasn't an emphasis by those who saw it?
However, IMV, John did make a reference in as much as Jesus was the example for all men. As you mentioned, the real Jesus and who he was, was not what they saw externally but who he was spiritually and thus, "His face shone like the sun, and his clothes became as white as the light." to which The Father said, “This is my Son, whom I love; with him I am well pleased. Listen to him!” (of course, there are dividends to listening to what Jesus said.
In reference to "transfigurations" we must realize that by nature, all of us have a nature to which our righteousness does not match God's righteousness as He said through His prophet, Isaiah "64:6 All of us have become like one who is unclean, and all our righteous acts are like filthy rags; we all shrivel up like a leaf, and like the wind our sins sweep us away."
Thus, as John speaks of a transformation, John 3:3 Jesus replied, “Very truly I tell you, no one can see the kingdom of God unless they are born again.”
4 “How can someone be born when they are old?” Nicodemus asked. “Surely they cannot enter a second time into their mother’s womb to be born!”
5 Jesus answered, “Very truly I tell you, no one can enter the kingdom of God unless they are born of water and the Spirit.
6 Flesh gives birth to flesh, but the Spirit gives birth to spirit.
7 You should not be surprised at my saying, ‘You must be born again.’
8 The wind blows wherever it pleases. You hear its sound, but you cannot tell where it comes from or where it is going. So it is with everyone born of the Spirit.”
So we are transfigured by God's own Spirit becoming, once again, made in His image and in His likeness... or, in other words, we have received a new heart
So, because of the work of the Cross where again, scripture tells us in Ezekiel 36:
26 I will give you a new heart and put a new spirit in you; I will remove from you your heart of stone and give you a heart of flesh.
So John spoke of the transfiguration that was intimated by Jesus Christ and as we believe in the work of Ps 22 and 88, the Father says "You are my beloved son in whom I am well pleased".
....and in doing so he couldn't get all of those details which he did mention correct. And why would he have mentioned making booze at a wedding, or causing criminal damage in the Temple, whilst failing to mention the real mission that Jesus undertook?
Well, neither of us are here to ask him but it did say "This is the
first miracle..." Maybe that was important?
The gospels told the story of the mission of Jesus, which apostle John didn't actually know about. And many of the details in his gospel are shown to be untrue when the synoptics are read.
Why do you say he didn't know about it? Do you have a reference? As John said, "21:25 Jesus did many other things as well. If every one of them were written down, I suppose that even the whole world would not have room for the books that would be written."
Obviously there was
much that he could have written about. Not enough time and papyrus?
Please show some verses which describe what Jesus and the disciples did that week, leaving the last 36 hours out of it.
Why leave the last 36 hours out of it? Is it because he was there? But as your request...
Please note the amount of times that John "filled in the blanks"... why? Because he was there. And you will notice that some of the other gospels didn't say exactly the same thing... they also filled in some blanks.
So why did Luke and Matthew add Mark's verses to their own gospels? And copy other verses as well?
Apostle John added to the story alright........ uncorroborated claims, Ken
There are some things in Luke, that Matthew and Mark didn't mention... so? Or... ask yourself a question, "How many letters were written at that time that said, "DON'T READ JOHN... IT IS ALL HERE-SAY OR HERESY". Zip, nothing, nada, nente, zero. Why? because no one had a problem with it.
None of the disciples were there, Ken. None.
Only Magdalene, Salome and some other women had the guts to attend, watching from afar.
Hmmmm.... How many of the gospels say that Salome was there? Only one? So... if I go by your standard, it is ok that John was there too.
If you witnessed a great event or events, you'd make mention of every detail, Ken. imo
If I was writing a complete biography. But John wasn't writing that.