I killed Duke Fishron 3 times last night in a single player, hardmode, expert game and he did not drop a treasure bag on any of them. I have gotten treasure bags from all other bosses that I've tried so far. I stayed in the ocean area where I fished him so he was not enraged. I use an arena so he was likely killed by traps or pets each time. Has anyone else had this issue? Is there a way to fix this?