I've set up a tile rendering system based on Mapnik + PostGIS. When I open the data with QGiIS directly from PostGIS it looks fine; but when I attempt to generate tiles with Mapnik they look stretched (notice that this issue only appears when the rendered tiles are on another horizontal line).
Tiles viewed with OpenLayers:
Tiles viewed with QGIS:
Raw data from PostGIS viewed with QGIS:
Can you please guide me trough what things should I check in order to fix this issue?