I own a project created with TileMill in SRS 900913. The data source is a Postgis database with the same SRS.
When I'm loading the file generated with TileMill (mbtiles) in QGIS and I'm putting under an orthophoto with the same SRS, or the original Postgis layer, the mapping displayed is moved approximately 2.5 meters moves in the Y axis relative to the PostGIS layer.
However if I'm loading QGIS directly from a PostGIS data source, works like a charm (think). Is like TileMill is displacing it because, as I said, loading the postgis layer directly from the database is working fine. In this image, you could see the Y offset between postgis (marked in blue), and mbtiles raster (marked in black)
Anyone know what could be happening?