I presume due to bad handling of the props we pass down to the BrainzPlayer UI, whenever the progressbar update, so do certain other elements of the player. In particular all the icons (FontAwesome icons) get regenerated (they have a random string in their class name) causing too many layout refreshes.
This probably slows down the UI too, since the refresh happens a little over once per second.

We should isolate or memoize or whatever it is youngsters do these days.