Why does the setting of Configuration device I/O voltage revert back to Auto?

Description

Due to a problem in the Quartus® II software version 15.0.2 and earlier, the setting of Configuration device I/O voltage under Device and Pin Options may revert back to Auto.  You may see this problem when you change any settings of Device and Pin Options except for Configuration device I/O voltage.

Resolution

To work around this problem, set the  Configuration device I/O voltage  after changing other settings. 

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