Yining:

(a) After you navigate to https://transitionbug-dot-shaka-player-demo.appspot.com/demo/?lang=en;play and the playback starts, if you click "Info" you'll see the current "Active resolution" is 320x240. If you wait for a while (w/o doing anything) you'll see the "Active resolution" is switched to 768x576, and the transition should be smooth. This is the normal transition case.

In your case, you choose a different value in "Video tracks", which I assume will cause the player to pause, fetch the new resolution video, append it, and resume playback again. The video will "freeze" in this case, which seems normal to me. (+joeyparrish to verify.)

So since case (a) above works as expected, I think this is a WontFix.

Manually changing tracks should take effect immediately.  To make the change immediate, we must clear the buffer, which causes a slight pause.

When changing automatically, the user did not initiate the change, so the effect can be delayed and the change can be made without clearing the buffer.

So this is all WAI.