I know you don't to hear this, but it sounds like you probably have a faulty digitizer on your hands and will have to source another. Just to be sure though, make sure all the connectors are properly seated. If it's a ribbon style connectors, trying cleaning the ends of it with a cotton swab and 91% isopropyl. If it's the FPC type, have a look at it under a microscope to make sure its not missing any pins