Shulker Box Problem

Hi Mojang, there seems to be a problem with shulker boxes. If I create a new world, they work as intended i.e. drop when broken but when I do the same in a marketplace world (City Life by PixelHeads), they do not drop. Please, could you take a look at this issue and if it is to do with the marketplace world could you try and find a workaround so that none of our progress is deleted. Thanks.