Hehe, sounds like a classic case of your navigator being shoddy in his plotting; taking you into a harbour wall or a ship or some such
I like to stay on the bridge and navigate the boat out of port myself, which avoids these problems, plus I like the view. It's not necessary to do that though; just zoom in as close as you can when you plot your course and ensure there are no obsticles near your boat (some things will only show up when zoomed in very close). Also bear in mind if your're plotting a very tight course round a harbour wall or whatever that your boat might not be able to turn as tightly as you've plotted, and could drift into the obsticle. Give yourself plenty of space!