Permanent Gaint Purple Slates and Broken Lighting

There is a permanent purple slate under every town in my map and I cannot remove it. There is also a lighting bug on my map making everything as bright as the sun when I enter a biome that isn't Starting Coast.
How do I fix this?

 

"There is also a lighting bug on my map making everything as bright as the sun when I enter a biome that isn't Starting Coast."
I'm having an issue where some terrain textures aren't loading, this sounds a bit like the results I get when playing the map in areas that has no textures.
Are you getting any "missing splat texture" errors in the server log?