Codex Vaticanus Graece 1209, B/03
General description of the codex:
My pet theory:
I think that it is possible the the codex has been washed off to create a palimpsest.
That a codex ink is fading throughout so strongly is quite exceptional. I think it is possible that at some point someone decided to wash off the ink to create 'recycled' blank parchment. For some reason it was decided later to keep the text and codex and someone had to retrace everything.
Well, just my private speculation ...