As I read other stair-related bug reports, I guess this behavior might be a result of the hitbox problem with stairs so the stair can't be attached to each other because it might think the stair faces the wrong direction for that or it is not a stair at all, not sure about that though.
As I read other stair-related bug reports, I guess this behavior might be a result of the hitbox problem with stairs so the stair can't be attached to each other because it might think the stair faces the wrong direction for that or it is not a stair at all, not sure about that though.