Sea crossing Arrows - Corfu

[Hawks5896]

Another strange event from our PBEM game has me wondering.

The situation: Russian corps on Corfu with captured Turkish Transports (10). Khan plus Turkish Corps in land area with crossing arrow to Corfu.
Swedish LT naval fleet in the sea zone of the Adriatic north of Corfu (the area containing the crossing arrow).
The game during the Turkish turn allows Khan to attack the Russians on Corfu - the Tirks are replused and Khan is captured.
Why, with my Swedish Fleet in the sea zone, are the Turks even allowed to cross to Corfu to initiate the battle - should they not be prevented from doing so? Do I not have my ships in the proper sea zone to prevent the crossing?

We are happy to have smacked the Turks but cannot profit by rules glitches. Does anyone have an explanation or any thoughts on this occurence?

Hawks 5896