I too am experiencing this same issue with my D750 files that are also 6016x4016.
The saved DNG file is 1024x683, hence unusable.
Using activated 7.7.5 Pro Lifetime

Helicon Remote is a standalone program, you can download its installation from the same Download page: http://www.heliconsoft.com/software-downloads/ Here is the link to Online help : http://www.heliconsoft.com/helicon-remote-help-online/ You have local copy also, just go to Helicon Focus main menu...