I had several farms, huge houses/builds, villager trading hall/breeder, mines, etc built on a jungle island. The entire island is now a regular jungle biome. All that is left is my creeper farm, which was built 100 blocks offshore, and the mobs/villagers themselves, which are no longer contained. Trained pets (cats, parrots) are still there as well. The terrain was reset, too.

Thankfully I have a creative copy of the world from several weeks ago, that's where the pictures came from of my original builds. There have been other farms built since the copy was made, but that's all gone too.

Leading up to this, I had left my person afk overnight to run my automatic pumpkin/melon farm I had just finished building. I woke up to a message saying Minecraft had run out of room, so I deleted an old Bloom world from over a year ago. When I reloaded the application and went back to my main world, I found it like this. 

Please tell me something can be done about this. I spent hundreds of hours on these builds, and I truly loved what I had created.

Update: since my creeper farm was intact I traveled to find my Nether Portals and other builds. They're gone as well. The only way you could tell I was there is the creeper farm.

Update 2: I found my cobblestone quarry and chests/Ender chest in tact. It seems like everything east of 367, 63, 87 was reset to the original generated world. I have no idea how something like this could've happened.

Update 3: The end dragon respawned along with another functioning end Portal on top of the old one... And all my Nether builds are in tact. Weird.