Are you running the most current version of MatterControl? The robo3d versions can be a bit behind the stable releases sometimes, so I recommend you download the current plain version from our site and try again: http://www.mattercontrol.com/#jumpMatterControlDownloadsIf you still get the same issue, please share your Model File, Slice Settings, and G-Code File using a file-sharing service like Dropbox and post the link in a reply on this thread. We can investigate and get back to you.