Bug: Killing the last horse rider with units still alive
There is a bug with the final round that causes the game to endlessly freeze (not hang, just stop progressing) if you by some happenstance kill the last Horse rider before killing all the mobs on the the map.
I was skipping levels so the Horse rider spawned just behind the last air wave, when the last bird got knock-backed I ended up killing the Horse rider first, then the game just stops no timer no bonus round display no missions completed.
Also a suggestion would be to add a "Wave Counter" to the bonus round (in addition to the duration one), just to make it easier to get a hang of how much armor they have.