When exploring, I tend to take the bells as souveneers I guess. Each time I have done this the game crashes. Villagers stop moving, I can't break blocks, I cant mount my horse etc. Lost a horse with diamond armour annoyingly enough one of the first time this happened. Couldn't quite work it out the first few times but I have just done it again and it is definitely the bells. When I then save and quit the game is stuck on the saving screen so I have to close the app down before starting back up.