In my StB game, cameron88 attacked Oranienbaum on Axis turn 2 (the first German turn), and the attack failed... but really it was a success, because it lowered the fort level. The defense there is not maintainable without the fort, so... If the scenario is intended to make it so that Soviets hold Oranienbaum, then it seems like it should be changed so it is not quite as easy for Axis to knock down the fort there and force Soviets to abandon it. Perhaps it should be a level 5 fort and/or the scenario should start with more Soviet troops there.
This was also with me changing the Soviet general to Fedyuninsky, the best one in the Leningrad area (he doesn't start out commanding Oranienbaum).