Prestek imaging issues

Writing this for a fellow employee to help find answers. We are Mac based using InDesign 6.0. Black background with images placed on top with feathering into background all assembled in InDesign. We are getting hard, unpleasant looking blends from the images to the background. More like banding issues it looks like. This is going to a Prestek 5034. Anyone have these issues before and have any suggestions on how to resolve?

Thanks