The Bug:
When I activate a lever placed on a full block, it activates the trapdoor, but when I activate a lever placed on a stair, it doesn't activate the trapdoor. The two screenshots I attached below show the behaviour.
How to reproduce:
Place a Lever on a Stair, then place a Trapdoor anywhere on the same Stair, and then activate the Lever.
Observed Behaviour:
Lever can't activate nearby Trapdoors when the Lever is placed on a Stair.
Expected Behaviour:
Levers can activate nearby Trapdoors when the Lever is placed on a Stair.
Stairs are transparent blocks and do not transfer redstone power. See MC-7335.