I placed 2 pistons, one on top of the other with a block on top. I then placed redstone on the block and powered the redstone. Both pistons extended. Only the top piston should have extended.

Steps to Reproduce:
1. Place 2 pistons, one on top of the other facing the same way (for me west)
2. Place a block on top of the pistons and put redstone on there
3. Power the redstone