I've encountered an issue with gerbers from the DesignSpark/EasyPC/Pulsonics family.
Their polygon fills don't include the starting coordinate, but instead assume the plotter will start at whatever the last coordinate was. For example:
Gross. I've submitted this as a bug to NumberOne Systems, since I think it's incorrect-- or at least ambiguous-- behavior.
If you load the attached file "Bad-Polygon-Fills.ger", it will look okay. Gerbv actually parses and draws this properly in the UI. Now save / export the gerber and reload it. Mutilated polygon city.
I don't know what the right fix is. Should the current photo plotter position be recorded as the polgyon start if there isn't one inside the polygon definition?