The exported collada file looks as expected, but when I upload it to Shapeways the processing adds material to my model in the preview image. It does not show up in the 360 view, just the image. The image that they sent me when the final print check failed also had some material missing. I used sketchup to create the file and export to a collada file. Their support team tells me that the problem is likely occurring when they use netfabb to process the image, but when I do this myself by applying an automatic repair, the file appears to be normal with no added material or other distortions. I would appreciate any ideas here. Thanks!
Can you share the model, or at least a picture of it ? Automagic addition or removal of material could be due to overlapping geometry (and I seem to remember from other forum messages that there are easy mistakes to make in sketchup that lead to just such overlapping features). Which path is chosen to "correct" the model might depend on whether one uses the free or the non-free version of netfabb (and in some cases the freeware version can only offer to highlight problems, but not fix them)
I haven't looked at your file, but the result looks like you have either open faces or overlapping faces. Our automated software will try to close open faces, and with overlapping faces our software removes one set, causing you to have a set of faces inside that it sees as open. So it tries to close them.
I'm guessing you have internal geometry in your Sketchup model. You'll need to find and delete those faces if Netfabb can't automatically do it for you. This article may help as well: http://www.mastersketchup.com/8-tips-for-3d-printing-with-sk etchup/