Overnight I was AFK in my world (as I had done many times before) and this morning I woke to find cliffs and other landscape elements had generated  haphazardly in the middle of my base (including my ENTIRE inventory, which is now completely gone).  I did not experience any crashes, had been playing on the updated version (1.15.2) for a while, and had plenty of computer resources to handle the load (FYI, Windows 10, 16GB Ram, Core i7, a few hundred GB free on disk).  Parts of built structures have been moved around (see screenshots–one of my castle towers was moved, the back half of the windmill is now in front of it, etc.)

This is devastating, considering the countless hours I spent building that world.  I even just yesterday beat the end dragon.  Please, please, please help.

(If this is an April fool's joke, I will admit it's kinda funny).