Okay, I have no clue how to explain this bug... I really feel dumb for not being able to. If you want to have any chance at fixing it or even understanding it, you'll have to go into the world that I have attached as a .zip.
So, I was just compacting a redstone project I made. It worked, but it had a quirk. If you powered it using any redstone component excluding redstone dust, a lever, or a daylight detector, it wouldn't work.
The aim is to make a two block high staircase. Try running the contraption that has a lever attached to the magenta wool. It works fine. Now try the one with the lever on the red blocks. it doesn't work. If you pay close attention, you'll notice that on the second one, the higher piston activates first to try push the stair two blocks, whereas on the first contraption, the lower piston activates first and works.
Why? I have absolutely no clue. There seems to be no reason that they work differently.
However, you'll notice a sign on the second contraption that says it works if you break the piston under it. Do so and the staircase works...
Yeah... I really don't have any idea. Sorry for lack of info.
Beethoven
maybe it's because you're hard powering the block?
(hard powering is when a redstone component is facing into a block
not when it has been powered by redstone dust.
Watch mumbo jumbo's video on it.