German Air power does not support offensive script.
Air is obsessed in attacking shipping with no tactical bearing on the script, also units across the Bosphorus.
Does not swap weak unit away from forts for stronger units.
Place non-combat units in combat situation, next to Allied fort.
With available combat unit next to the Engineering unit.
Allied fleet goes on kamikaze attacks on the north shore.
As if the system does not recognize the German massive air superiority.
Also, in the English Channel. Whole country fleets have been lost for no tactical reason, with no naval battles.

(Not an error but thought. Keep shipping away from artillery.)
(It appears when shipping is choosing between two hexes pick the one next to the artillery.)
Here are two saved games to review the situation.
https://www.dropbox.com/t/ejb5WMtafUnQbuJW