Hopefully someone knows something about this. I've observed it, and tried to test it as best I can, but I cant figure out what the problem is.

Challenge Levels 1 and 2, used to give Fire and Sea rewards. Challenge 3, never did, least not for me. Then 1 and 2 stopped. Took me awhile to notice. I started going back and forth on challenges and campaign. And then, 1 and 2 started giving rewards again. Not sure when or why, but after at least 10 times, they have now once again stopped providing the special upgrade items when destroying the boss. I dont know what caused it or how to undo it.

Anyone else having this problem? Its erratic nature makes me think its not something planned like after X turns, you can no longer do it, but hey, maybe I'm wrong. Any info on this occurrence would be appreciated. Thanks.