After a Shulker box is placed, when I leave the game to answer a phone call/text message, I find the Shulker box to have completely disappeared.  This problem has been an ongoing issue for over a year now and have seen at least a dozen boxes disappear in this manner. Last night’s occurrence was the third “gear” box (full of netherite tools and replacement armors) to have disappeared on me, all enchanted exactly how I preferred.  

I have read that this issue continues to be addressed during the release of multiple hotfixes in the past, but it has yet to be resolved.