It's not a bug with the server, it's a bug with the world not rendering it all, it happends to everyone, it's not a server bug, it's a minecraft bug itself.
I think it is like that because there's a roof above your platform you are showing us. Not completely sure though.
By the look of the video, you have shaders on? If I'm correct, it could be a rendering bug with your shader pack.
It's not a bug, and I'm pretty sure there is no fix to it. This has happened to me too, I'm pretty sure its just the lightness that isn't rendered all the way until you get close up to it.