Dear UE gurus
Does anyone know why I am getting corrupt lightmaps ?
The mesh doesn’t have overlapping UV’s and the lightmass resolution is 1024. Also lightmap compression is turned off.
Try regenerating the lightmaps in the Mesh Details.
That’s what I have done, I have an unwrapped (flattened) set of UV’s in channel 0 (from 3ds max), then I let unreal generate a new set of co-ordinates in channel 1 (based around a map size of 1024).
Try changing the mesh in 3DS… maybe make it into different parts/groups. I’ve had issues and sometimes that’s the solution
OK I’ll try, its exported as a single “poly mesh” from 3ds max. with the elements as separate sub elements - I’ll try exporting with a different “topology” if that’s the right word 
Can you show us the layout of the light map? And make sure you changed the settings of the mesh not only in the build settings but also further down in the static mesh settings. The lightmap id setting is a bit hidden. Often when you automatically generate lightmaps an additional id is added but the resolution and id stays at the old settings. The build settings where you generate the lightmaps are not the mesh settings! It makes sense when you see it.