Lose the twist ties and replace them with something softer. Sharp edges can cut into the plant and let infection take hold.

I think the white bumps really could be root nubs. Are they shiny looking? Is your humidity high enough for the plant to try to air root?

And this one I am just guessing, but if you put a tie like that on too tight, does it work similarly to how when you want to air-layer a plant, you have to make a little slit in the bark where you want roots to grow?

At any rate, don;t scrape the bark off.