Exporting and importing design partition

Thanks for answering. I understand that it has something to do with double pin assignment. But the case is there is no pin assignment in the first (exported) project. At least I did not assign any pins. Is this happening automatically during generation or exporting because I have chosen a certain device Should I remove the chosen device too. Or Should I remove also the pin assignments in my big project where I instantiate or import the created partition. Thanks again.