Some possible explanations as to why you're missing with a good "lock."
- Gyro angle too large
- Torpedoes set too deep
- Torpedoes hitting the target at too steep of an angle and bouncing off
- Torpedo net or other obstructions in the harbor (The draw distance in the program can screw you up here... I've seen ships through my scope that appeared "out in the open" in a harbor, when there's really a pier between me and the ship. I think the non-ship stuff has a shorter draw distance.)
I sometimes do a little harbor raping, but they usually shoot back with machine guns once they spot me. It does seem a little too quiet in the harbor when you're doing this though. I guess they didn't put too much into programming a realistic response to a harbor attack. It would be cool though to see all kinds of activity when they realize they're under attack.... alarms, search lights, etc.