Here http://osm.org/go/0DddSTeIv- the B 42 (national road 42) ist the left red road. Just right the one-ways are "Link" Roads (from and to B 42). MF (Android) routes over the link roads if you just want to follow B 42 direction north.
In Germany highway links don't inherit the speed limit from the main road so they often have no speed limit. I added a highway=give_way but I doubt it will help. Mapfactor should rate links down or consider the junction more. Mapquest/OSRM/Graphhopper are dong this route fine.
Saying that is not nice Oldie. Maybe you and Dave are right and there is a security issue I did just not encounter before, but this is not a reason for telling me I should pass my driving licence again.
I'll not elaborate further as this would be feeding a troll.
Instead of just strolling on B42, you leave it, you have to give way to the crossing road (Siebengebirgsstraße; i.e. look left and right for other cars, bikes etc. coming) continue again down to B42 and give way to people coming on B 42; instead of having priority with proper routing of MFN.
People who say, this is not a security issue, should return their driving license :-o