Ender Chest vanished while retrieving it in new nether biomes

After a solid afternoons searching for Ancient Debris under one of the new biomes, the Shulker box i was utilizing while collecting items I placed back into my Ender Chest in an opened up area and vanished whilst attempting to retrieve it. My inventory was practically empty as i was just about to start mining back to the surface,  so i had just removed my respawn anchor etc. too. It's a bit frustrating considering what i lost in the process but i thought it needs to be raised as like most people i use it as a safety measure should i die for whatever reason, but if i can't rely on them it's going to make life in the nether an absolute pain. if they have become unstable in the nether update. I have only used my Ender chest in my already established base until now since the update. I'll be testing it a few more times with items i care less about in similar areas. 

 

Thanks 

 

Toons