I have 2 separate deployments for Graphopper directions API with same configuration file. The only difference is that one uses whole US and the other one uses only Maryland. For some routes, sometimes both are giving me different results.
Can you add a via-point to enforce the straight route (the one you get for the US instance) also on your MD instance? Does it yield the same time and distance as for the US instance? And is it even shorter/faster than the route you get without the via-point?
For things like this it also helps sometimes to enable ‘Local MVT’ in the map’s layers menu. It might take some time to load, but it will display GraphHopper’s routing graph. So you would probably see that DC is missing.
One of our goals is to get rid of this discrepancy and hopefully this pull request https://github.com/graphhopper/graphhopper/pull/2637 will make this possible. You could already try this branch to slow down the speed in the city center. And if you do please do not hesitate to share your results here