Currently the MapnikRasterizer will not render lines/polygons if the output raster dataset exceeds ~32,800 columns - text and points will render normally regardless of the size.
For example, if I try to process a dataset that spans 40000 x 45000 pixels, the output will be missing the rasterized lines past column 32,768.
The current workaround is to use a RasterTiler before the MapnikRasterizer. You can then use a RasterMosaicker following the MapnikRasterizer to combine the tiles into a single mosaicked dataset.
If this impacts you, please add a comment to this post or submit a case referencing the following issue reports:
By submitting a case with the references listed above, you will be notified as soon as the fix becomes available.