as you can see not supposed to be activated piston

Please do not mark unreleased versions as affected.
You don't have access to them yet.

I can see nothing.
Or something like a wall of coalblocks.

--> Please make screenshots at daytime.

This is called Quasi-connectivity and is likely a completely intended feature.

This is a highly useful quirk of redstone. You have to get used to this kind of thing when playing Minecraft.