Yes it only happens on device. Simulating routing via:
http://www.openstreetmap.org/browse/way/310376420 will in this case not switch off the device, but just get stuck. Map moving forward/backwards slightly.
Here you could reproduce it by simply doubling the routable lines - one routable line for highway=path, another one for the relation route=hiking or route=mtb. 6 Routable lines (which are not oneway) with exactly the same way on top of each other are enough to reliably cause the Oregon 600 to break routing in my experience.
The arc list actually helped me to identify some common problems in my style so I could reduce some routable lines - but in my experience adding several lines on top of each other - with different road_class/road_speed helps prioritise those ways. For highways this is not needed - as they are straight. But with mountain pathes - often a road_class 4, road_speed 2 is already too high importance to be chosen for curvy pathes, so adding a road_class 3, road_speed 1, and road_class 1, road_speed 0 will help to prioritize such ways. Also adding relations as routable lines often helps in so far that at least according to gpsmapedit they have much less routable nodes than the underlying way - so maybe that helps prioritizing them too?
Felix