A bunch of chunks in our Realm went missing. No blocks, including bedrock. Lava and water at the edge of those chunks aren't flowing into the void.

Some chunks in the nether got reset to their default state. 

A section of another chunk (y ~80 to ~130?) were removed from the middle of my raid farm, leaving floating scaffolding in the air with nothing supporting it.

About 70 mb dropped from the world size.

I have a world download from both before and after if those are useful, but they are ~900 mb each