Unable to double tap an item to stack them anymore.

You used to be able to double tap an item to quickly stack them but this no longer happens. Gold is also unable to a smelted?! Fortune pickaxe doesn't work on anything anymore diamonds coal the lot. Villagers are occasionally changing profesipns evne after I've traded with them initially. They somehow keep their levels though. When I minimize the game there is a chance I fall through the world and die In survival?