Stair Lighting NOT RESOLVED

Stair Lighting

What I expected to happen was...:
The stairs to look normal

What actually happened was...:
I was showing my friend the red stairs and when I made the curved stairs and had blocks behind all of the stairs the corner stair's transparent part became dark

Steps to Reproduce:
1. Make curved stairs with curved upside down stairs on top of them
2. Place blocks behind ALL of the stairs even on corners and edges
3.I know it is a copy of MC92 but MC92 says it is fixed but it isn't
P.S. It happens with all kinds of stairs