On openstreetmap.org you can use the routers by right-clicking on the map and select “Use as starting point” and “use as endpoint” (translated by myself, I see “Route von hier” and “Route nach hier” in german).
After doing this, green and red route markers appear and the route is displayed between them. Unfortunately, the red/green markers do not appear exatly where I did the right-click, but somewhere around. In residential areas the marker is often pretty close to the original location, but more remote, for example in a wood, it often jumps too far to be not usable any more. I cannot tell exactly how this “jumping” works, but I guess it is some reverse geocoding. In the from and to fields on the left side, it does not fill in coordinates but addresses / names.
Example: Take this link and right click close to the green route marker an select “Use as starting point”. It will jump and give this result.
As workaround, you can pull the red/green marker by drag and drop to the location you previously selected.
Has this bug been discussed somewhere? Or is it a feature?