It wasn't until I came to this thread I realized there was more, and I should look again, but even then it took me forever to:
1. Realize I needed to put my hand on my mouse, hover the tiny, thin red line to get it to expand, and then use that to navigate.
2. Flip between pgup/pgdn and arrow keys. Sometimes one set worked, sometimes another did, and it would flip at random points in the experience.
Why on earth would you selectively enable and disable the browser's interaction with common navigation keys repeatedly in the span of a single page? I can understand blocking/swallowing one set if you intend to use it somewhere for something else (i.e. the text input sections), but flipping them on and off with no other use for those keys while they are blocked? It boggles the mind.