Altium Gerber export fails
Please see:

Exporting fabrication files (gerber) in Altium leads to wrong connections

for a possible solution.

Quoted below:


  When you view the files in Camtastic, you are already viewing the
  Gerber files. Camtastic is a "Gerber File Viewer and Editor".
  
  You do not need to export anything from Camtastic.
  
  After you generate the Gerber files (typically done using an 'OutJob'
  file), simply open the output folder in your project files (using
  windows explorer), and zip up the output files you need to send to
  your pcb manufacturer.
  
  You can use Camtastic to view the generated Gerber files, and
  pseudo-independently confirm that they are ok and conform to some
  rules (see the Camtastic analysis menu).
  
  Sometimes, in rare and advanced circumstances, one would want to edit
  Gerber data using Camtastic, and re-export using the tools in
  Camtastic program. However, this is really unusual now-a-days, and I
  have not had the need in a decade.
  
  Camtastic can be used as part of the process to reverse engineer
  Gerber data back to a pcb file. But this also is an advanced and
  unusual requirement.
  
  'OutJobs' are your friends. You'll be happier if you use them.