When you are shifting on top of soul sand you cannot place over the face you are hanging over, soul sand will work but any other block doesn't appear to work. Maybe this is just a feature, but I don't remember this ever happening before and it doesn't seem like something that would be intentional, and the wiki doesn't say anything about this. I feel like it didn't work in other situations when playing survival, but this is the only one I could replicate on a creative world.

What I expected to happen was...:
It should place a block down.

What actually happened was...:
The block is not placed.

Steps to Reproduce:
1. Place piece of soul sand
2. Jump on piece of soul sand
3. Shift over a side of the block and try placing a non-soul sand block on to the face you are hanging over, the block doesn't place if it isn't soul sand. Bedrock, grass block, netherrack or cobblestone won't place obviously I'm not going to test every block, I'm guessing it doesn't work for any block except soul sand.