Open shapes can be a printer's worst nightmare. Not sure why? We recommend you check out this article: Points and Paths: What's the deal with open paths. Please make sure that you are properly closing each shape as you're drawing. The standard shapes in vector software (squares, circles, etc) will automatically be closed for you, but you'll need to pay attention when you're drawing your own objects. Check your images carefully in outline (also called 'preview' or 'keyline') view to ensure that every shape is closed, with no breaks, holes or gaps in the outline.
Please note: Transparency effects (transparent objects, glows, drop shadows, etc.) aren't compatible with the AI8 EPS format. Saving a file with transparencies as an AI8 EPS can cause your shapes to break open and color fills to flatten and 'rasterize'. We ask that contributors avoid transparencies in their submissions to iStock. For more information please read this article: Are you compatible?