Stack some loose cinder blocks around the dock and see if it still finds it's way to it?
I used to run a Friendly Robotics RL800. It was an older model, it was wire-guided and just ran until it had 10% or so of the battery and would just stop wherever it was. You had to drive it home with the joy stick (again, early model with no homing function). So I have some robo-mower experience, but not ones that go home by themselves.
