Hello, I've noticed the bug.
As the screenshots show it only works (Or isn't working as its the bug) with "going down" redstone on the 'Minecraft:snow' (full) block. (It is normally working on 'Minecraft:snow_block').
So in the longest shortest description: Redstone is not charged after contacting the snow so it can't reach the piston to make it raise.
(Note: It is really important to use the 'minecraft:snow' [the one that you need to place 8 times to create a block to recreate the bug])