Any time I try to open an Enderman's chest or the dragon's chest, it doesn't let me

in the newest version, if a mob has more than 10 hearts and is over half health you cant open them. this is to prevent you from skipping a fight by removing vital organs

I actually like this. It'd feel anticlimactic to kill the dragon by popping out her heart.

I have noticed that all you-can't-open-this-mob's-chest sounds are subtitled as "turtle shell thunks", but that's minor. I soon worked out what it means.

As A5tro said, this is not a bug.