Not sure if this is a BTW problem, but thought I'd post here to see if anyone else is having this issue.
When placing a piston towards powered redstone, it creates a piston on the bottom, pushing the block under it down.
Unable to reproduce here in both vanilla and BTW. Do you have any other piston mods installed?
And what is that on the back wall, to the left?
"That's the nice thing about mods. There's something for everyone. Some of us like to build functional elevators, while others want to run around with a bunny on their head."