Basically the title. This is caused by how texture is made (I mean, bugged texture have only borders, because I'm using connected bookshelfs txp), but it is a bug, because:
1.It worked well in pre-3
2.The only broken sides of it are west and east, even if it was added to every side face and on those sides "higher" texture makes "lower" completly invisible, what means this could be spotted with any other texture that uses method of this kind.
I somehow didn't notice that it was broken in pre-3 too