Ender chests and shulker boxes, sometimes ranomdly deleted when mined.

Occaisionally when mined my ender chests and now even shulker boxes will delete themselves. I always mine my Ender chests with a diamond pickaxe with silktouch and my shulker boxes with iron pickaxes. not always or even a majority of the time but about 5% of the time they disappear completely. not so bad with the ender chests, just make a new one and I can get my stuff, but now i see a shulker box do it, and im very disheartend. I can't easily replace the shulker shells or the contents of my exploration shulker. lost several stacks of firework rockets a saddle and some horse armors, my woodland and ocean explorer maps, a minecart some empty maps and compasses. now i'm afraid to mine any ender chest or shulker box i place, even though that's supposed to be their function.