Of all the 3D modeling programs with which I am familiar, SketchUp has the worst track record for creating printable models. I did not download the file from the links provided, but it's likely that your model has a number of STL failures, which can include reversed normals, self-intersecting faces and other problems.

Consider using an online STL repair resource to see if the file can be salvaged. Sometimes the failures are so severe that there is no repair possible.