Unfortunately, the robot's performance is awful, resembling the circular meandering of a drunken butterfly.
I whipped up a Processing program to graphically display what the robot thought it was doing.
In the video capture, Data Bus is the green ellipse. The white line shows reported bearing to the next waypoint, depicted as a red circle. All other waypoints are blue.
It appears to me that the robot is over-correcting when trying to steer to the next waypoint. It's also possible that the steering control is lagging too far behind the position and bearing estimation.
At least now I have some idea of what is happening.
Current in-development version of the Processing program is here.