That's good to know, thanks. But I checked those, and I'm still having the same problem. I never add()ed that sprite before, so that's not it. For the persist property I added the following line after line 31 in Achievements.hx:
currentAchievement._icon.graphic.persist = true;
But that didn't seem to fix it. I'm still getting the same error.
lime test starts a local webserver, EADDRINUSE means that the address is already in use. Usually this happens when there's still another lime test command running elsewhere (in which case http://localhost:3000/ would still respond).