Why does my .qsys file contain lots of repeated _originalDeviceFamily elements?

Description

Due to a problem in the Quartus® Prime software version 15.0 and earlier, you may see that your .qsys file contains the following element repeated many times.

   element <Qsys system name>
   {
      datum _originalDeviceFamily
      {
         value = "<device family>";
         type = "String";
      }
   }

Resolution

This problem has been fixed beginning with version 15.1 of the Quartus Prime software.