HFSS Non-Manifold Edges error

Hi, I am currently working through validating my device design and am confronted with the error message "Non-manifold edges found for part..." I understand the definition of this message and have read that to overcome this problem, I ned to ensure the components overlap so they can be united/intersected. I have a series of Aluminium components along my device (used as contacts mostly) and my question is that if I unite these to the device, will the electrical properties alter? I have Aluminium atop Silicon Nitride and in some places on top of glass. Is the only solution to this Non-Manifold edges error to unite ALL of these components to my device? Any suggestions, greatly appreciated.