Yeah, there has been a changeset in spelling rules
https://de.wikipedia.org/wiki/Reform_der_deutschen_Rechtschr...
... several times: 1996,2004,2006,2011,2017.
The current correct spelling is either Schiff-Fahrt or Schifffahrt.
Impartial foreigner here who has no stake in the old or new spelling. If you're combining ship and port, you can't just write shiport. Of course it's shiff-fahrt / shifffahrt? By what logic does anyone argue anything else?