I was in towny and decided to protect my Hogwarts items by placing them into a shulker box. I placed My wand, my Pande doll, my Hari doll, my broom, several gobstones, several books, floo powder, and a stack of 15 cauldron cakes.
I broke the shulker and went about my business.
When I reopened the shulker the cauldron cakes were unstacked and some of the items that I put in the shulker were overwritten. The only items I care about that were lost are my pande doll and my wand.