Shulker boxes deleting all items it contains when loading world again.

I log out of my Minecraft World, (with shulker boxes that have been newly added to the world in the Snapshot 18w46a), and when I returned later, I go to get the items I placed in the shulker boxes but they are empty. After I noticed this, I tried it again two more times with the same result.  I do not believe they are invisible and nameless, I believe that they have be completely deleted.

 

Thanks anyway. Really looking forward to the full-release of 1.14.