I am using Mapnik to create tiles on a tile server. I'm depicting sea level rise in North America using SRTM data, and it works fine in most of the continent. However, when zoomed out in my browser (zoom levels 5 and lower), I get a peculiar horizontal stripe across the entire continent:
When I am zoomed farther in, this stripe does not appear, which makes me think it's not an issue with the data itself. The stripe is from 51 degrees N to 52N. I suspect it's some sort of projection issue, but I'm not sure how to troubleshoot.
Mapnik is being used with Tirex; it is reading from a .vrt file which in turn references ~2400 tifs.