Saving the world while in crawl mining position makes you lose half a heart when you load back in.

Saving the world while in crawl mining position makes you lose half a heart when you load back in.
Occasionally, you might suffocate and die until you mine the block above you.

How to reproduce:

1. Create a survival world.
2. Get a pickaxe (any type) and trapdoor. You may want a light source with you or night vision effect if you want to see better.
3. Dig down.
4. Go in crawl mining position.
5. Mine the blocks that are in front of you.
6. Save and exit the world.
7. Load back in.

Expected results: 
No hearts lost and player may continue with mining.

Observed results:
Player will lose half a heart and in some cases, suffocate and die until the block above the player is removed.