Crop Circles

[Mobius]

I noticed I was getting circles of clear around my woods and light woods. When woods are inside a light wood area there were always circles around this. I tracked it down to areas of the light woods and woods being shaved off so they no longer butt up against each other.

I overlayed the light woods terrain mask png to actual terrain bmp and they don't match.
This is MM0.9e and all textures with mask blur of 0.0.