Steps to Reproduce:
1. Get some slab and any solid blocks (example a dirt,grass,stone,etc.)
2. Place 3 solid blocks and a solid block above and place a slab below
3. press shift and sneak the forward on the build

Observed Results:
The player suffocate due to the full block above when sneaking

Expected Results:
Like sneaking above the slab the player won't suffocate