Flash of disabled buttons

Right now, when the user clicks on a button from the Yes/No/I Don't Know button set, all buttons are temporarily disabled as the page navigates to the next question. The disabled buttons look slightly different from the usual buttons, so there is a flash of different styling on those three buttons that lasts about half a second.

This is fine... EXCEPT the "Back" button doesn't get the same flash which is weird. I'm not sure there is some way to fix this, but it would be nice to have the "Back" button act in the same way as the rest of the buttons. This is a nice-to-have, not essential.

Start by locating the Yes/No/I Don't Know and Back button implementations and compare how each button is disabled during navigation. Reproduce the transition, then consider the issue done when the Back button has the same visual behavior as the other buttons without a styling flash.

Written by the indexing model from the issue text.