Using my own style and mkgmap default style (r3650 and previous releases) I struggle with an odd routing error on Garmin maps while routing between N37 52.116 W25 48.576 and N37 52.120 W25 48.573 (its on Sao Miguel Island on the Azores).
I checked the OSM raw data with JOSM and found no reason for that behaviour. I guess, node
http://www.openstreetmap.org/node/1838670264 causes the problem.
I use the PBF file from geofabrik (
http://download.geofabrik.de/europe/azores-latest.osm.pbf ) and tried different versions since Aug 2015.
The error occures on Mapsource, Basecamp, nüvi2xx, eTrex Vista and 30 (so I guess its a general effect).
But, when I load the img file to GPSMapEdit 2.1 and test the routing graph the routing works fine.