a strange and invisible block

Put the summary of the bug you're having here

What I expected to happen was...:
when you put a rock wall and put up two blocks of sand and break the front row is a rare block if you get up you get into it and is like a slab if you put blocks around

Steps to Reproduce:
1.Put a rock wall
2. put 2 blocks of sand
3. break the first row
4.and put on the player on the blocks

you can not break the block!
🙃