Lighting problems on ceiling with imported Rhino file.

I’m having issues with my ceiling. Some panels are darker than others (see attached pics). I went back to the Rhino model to do some tweaks to the geometry just in case how I built it was causing the problems. Re-imported the file and a different set of ceiling tiles appeared dark. All ceiling tiles have the same material and very similar lightmap resolution (red) and the lighting quality is set to Production.

Anyone have any ideas what could be causing this?

Many thanks in advance!


I’ve found out where the normals get altered.

Below are two snap-shots of the geometry in world normal viewing mode - the first being just after import and the second one is after I’ve applied a Substance material.

Seems like the application of the material is changing the normal.