Here is what I think. And the more I look at it, the more I like Alphahorn's Leading diagonal idea: Monday midday update, updated for the close.
Also, I did an extensive study of Wave 1's and 2's within P1: see O Mandelbrot, O Mandelbrot. And Minor 1 of Int 1 of P1 was a leading diagonal. In fact, there is quite a lot of similarity to the pattern. See this chart: M1 of I1 of P1