Files that are unable to be processed upon export (primarily non-CAD files) are able to be downloaded through the Onshape tab context menu. You are able to download any tab that is able to be represented as a file.

Download copies the file in its current format to your local machine, giving it the same name and file type. You are able to import and download any non-native file type into and out of Onshape.

The download location is browser-specific. If you'd like to be prompted to save to a different location, look in your browser settings for an option to Ask where to save each file before downloading.