Had this a few times, same outcome and easily reproduceable.
GNN News appears, inside it says a starport is ready.
Click goto (planet of new starport) in GNN screen
In planet screen click build ship top right of screen
It then takes you back to the GNN screen
If you click goto (target planet) again inside GNN, then you are sent to the shipbuilder, which is where you wanted in the first place, but on the second try you actualy clicked on goto (target planet). Seems like two errors in one here .... dont know.
Regards
Zy