In this specific case, the issue is due to a custom junction not having the start and ends far enough apart.
To resolve the issue, ensure that the start and ends of the custom junction are far enough apart. Then, in the maneuver road tool, confirm that all maneuver roads have the "Lock Geometry" option selected in the Attributes Panel. (This is most important.)
You should now be able to export to OpenDrive after rebuilding maneuver roads.