Hillshade & relief offset from the map

I have been using this docker image as a quick start to get a tileserver going. I have compared the included scripts against the instructions at https://github.com/der-stefan/OpenTopoMap/blob/master/mapnik/README.md and they check out. But the resulting tile server has the relief and hillshade offset a few kilometers north east.

Note the white band to the left. It's not snow (:

Contour lines seem to be at the right place, but the relief is offset.

This is the same location in opentopomap.org

Both the contour lines and the hillshade & reliefe are derived from the same SRTM data via http://viewfinderpanoramas.org/Coverage%20map%20viewfinderpanoramas_org3.htm

I have merged the files into the raw.tiff with gdal_merge.py -n 32767 -co BIGTIFF=YES -co TILED=YES -co COMPRESS=LZW -co PREDICTOR=2 -o ../raw.tif *.hgt.tif

Wraps with -tr 5000, 1000, 500, 60, 30 with gdalwarp -co BIGTIFF=YES -co TILED=YES -co COMPRESS=LZW -co PREDICTOR=2 -t_srs "+proj=merc +ellps=sphere +R=6378137 +a=6378137 +units=m" -r bilinear -tr 60 60 raw.tif warp-60.tif

Reliefs with gdaldem color-relief -co COMPRESS=LZW -co PREDICTOR=2 -alpha warp-5000.tif /home/otm/relief_color_text_file.txt relief-5000.tif

Finally hillshade with

gdaldem hillshade -z 7 -compute_edges -co COMPRESS=JPEG warp-5000.tif hillshade-5000.tif
gdaldem hillshade -z 7 -compute_edges -co BIGTIFF=YES -co TILED=YES -co COMPRESS=JPEG warp-1000.tif hillshade-1000.tif
gdaldem hillshade -z 5 -compute_edges -co BIGTIFF=YES -co TILED=YES -co COMPRESS=JPEG warp-500.tif hillshade-500.tif
gdaldem hillshade -z 2 -co compress=lzw -co predictor=2 -co bigtiff=yes -compute_edges warp-30.tif hillshade-30.tif
gdal_translate -co compress=JPEG -co bigtiff=yes -co tiled=yes hillshade-30.tif hillshade-30-jpeg.tif

What is strange is that the contours seem to be in the right place, while the hillshade and relief are not. I got the contours with phyghtmap -j 12 -o contour --max-nodes-per-tile=0 -s 10 -0 --pbf warp-60.tif from the same data that I derived the hillshade from. I would have expected all of them to be offset then.

I first tried with the complete South America pbf and SRTM for full coverage, which took days, then again from scratch with just Uruguay and only the Uruguay SRTM files, being the smallest filesize and quickest to redo. Both times the same result. Is this a misconfiguration of the map & server or an issue with rendering?

der-stefan / OpenTopoMap

Hillshade & relief offset from the map #326