i've logged a bug
https://bugs.kde.org/show_bug.cgi?id=278656

basically it's a showstopper for me. i'm using the map of ireland, and while marble/monav draws the route on the map, most of the turn by turn instructions are missing.

i've downloaded the offical monav gui from the monav website (which isn't in the repositories) and it gives the correct turn by turn instructions, so i don't think it's a monav problem.

i've even hacked the offical monav gui maps into marble and it's still the same for ireland.

i wouldn't feel confident planning a big european road trip with marble as i would have no idea when this bug would appearin other areas.

EDIT: i've confirmed the problem for some areas in Berlin,Germany. the offical monav navigation gui is fine, but marble's integration with the monav routing daemon seems broken. the semi-common way to reproduce the problem is to include a route that includes the intersection of 3 roads, i.e. a 'fork' in the road (i.e. a 'Y' shape). small (minor) roads, especially. to reproduce the problem, plot a route from the top of the 'Y' down to the intersection and then back up to the other top of the 'Y'. it doesn't work for every 'Y' intersection, but does for many. marble plots the route on the map correctly, but driving instructions ignore the turning and tell you to go straight on.

EDIT2:after more experimenting, the problem seems related to street/road names. if the streets/roads have the same name or have no name, then marble borks. is marble relying on street names for turn by turn driving guidance?! that's pretty optimistic..