Minecraft shader: leaf shadow disappears?

I have the shader "Sildurs Vibrant" and have recently had the following problem. On my two worlds, when I look to the west I have the problem that the shadows of my leaves disappear. First everything is normal then, I look in the west and zack away all the shadows of the leaves (for the whole world. Not only in the west). When I create a new world, I don't have the problem. And only the leaves. Everything else has a shadow.

I have already downloaded the shader again but it did not work.

I play on the 15.2

Can someone help me on this?

I think that's because of the shader that there's a problem