Yeah, just in case, I always do the full build.
About the terrain, I tried putting lights in different areas of the map but same issue (in the first pic you can see two more point lights in the back, with the same issue).
About the volumes, I tried switching absoultely all of them on and off and building, but no results. Anyway, I just have the Lightmass Importance Voulme, an Precomputed Visibility Voulme and a Postprocess Volume.
I havn´t made any changes on the project lighting settings.