Great game! One possible bug?

Great job! Thoroughly enjoyed this game when it was entered into Pyweek, and have been enjoying the post-Pyggy bugfix release.

However, I'm trying to output a 4x4 panel of Phrisbees, and running into trouble. I put Phrisbees on a QA machine, and they're being rejected, but when I inspect them, they look perfect. I can't figure out what's wrong.

I saved the game file to see if you might find it helpful:
http://hanclinto.com/dav/Clint/4x4PhrisbeeBug.alg

Thanks!

--clint