Normal Vista causes strange triangle shadows on main map

[FoozleMcDoozle]

When applying a vista normalmap to a main map it seems to cause these strange triangle/polygon shadows on the terrain,

the first image is with the normal and the second is without, the map specifications are 16x16-132-512, the normalmap is set to not compress when being imported

 

[FoozleMcDoozle]

issue seems to have been exclusive to the editor, when testing on the main map ingame there was no (or very little) normal issue