A very large light map

I appear to have a problem with area that's resolution is very large. Room that has 2048 x 3072 resolution background also has same size light map, however within the game character appears completely black instead of corresponding light map color. Problem is fixed when light map gets smaller (if height is closer to actual game resolution) however constant light map swap ain't option for me because of light map displacement.

the lightmap should be much smaller than the scene because it needs a lot of memory and the difference of a smaller lightmap is usually not recognizable. The lightmap will be scaled to the actual scene size (e.g. if scene is 1000x500 and lightmap is 200x100 then the lightmap is scaled by a factor of 5).

Oh my! Thank you for clearing that up. It seems I've got some cleaning up to do!