VRT in mapnik doesn't work correctly

[mar0321]

Hi,
we used to do Hybrid map via Mapnik, using orto rasters (JPG) and some label layers. but since mapnik 3.0.23 output rasters are incorrect. Ortomap from vrt. is blurry and the resolution is damaged. Any ideas? Im sorry it might be not related to mapnik but. Before that we used mapnik 3.0.12 and everything was fine.
Strange is that when we use single raster the output is fine and also when we build VRT just with one raster(ortomap) the output is also correct.
Thank you for help, mutch appreciated