Twice now when loading up my 1.9 world I've found areas of deleted blocks. At first I thought this was a chunk issue, but the second time it happened it didn't affect the entire chunk.

I've included screen shots, the first two being the first time this happened. That time, the back wall of my fishing farm and some trees' trunks were gone. There was also a dirt block replaced that I had previously removed. As you can see, the water didn't update. Also, the leaves left behind didn't despawn until I updated them. This time, the affected area fell right along a chunk border.

The last two screen shots are from the last time this occurred, and more trees were affected. Interestingly, the top parts of a large tree were left this time. This time I also happened to be looking directly at the affected area when exiting the game, so I know that this happened when I loaded it back up.

What I expected to happen was: The world to be the same as I left it when I started the game again.

What actually happened was: Blocks I'd placed were missing.

I'm sorry, I'm not sure how to reproduce this. I don't know if it has something to do with the trees or not. I do know that the area isn't affected until I exit and re-enter the game.