Edit: sorry I didn't realize that you found the bug already until I re-read your post. Thanks for confirming that the rod is the end for now.
no I mean if you interact with the chest after getting the crown back from the girl, then it triggers the same dialogue as when you first got the whip, and removes the crown from your character.
Or if you've delivered the crown to the queen and come back to the blacksmith (I was checking to see if she'd sell me stuff yet, and wondered if opening the chest started a conversation about selling stuff.) The chest also triggers that whip conversation. Which then triggers the requirement of the crown to use the boat, even though you already finished the quest line.