After several puzzles I ended up with open chests, so I couldn’t get any reward from them. I got the achievements but the reward chest was open. This happened today at the underwater organ puzzle too, the shell opened, but the chest inside it was already open (I never did this puzzle before).
I heard and read at several places that others have this kind of bug too, but I couldn’t find a common topic for it, only dedicated ones (for specific puzzles). A fix would be cool, because there are a couple of puzzles which takes time to solve, and they are fun and all, but seeing an already opened chest is not the best thing.