Nikon today issued their formal service advisory for the banded flare problem on D750 cameras. Check your serial number in the US on this Nikon D750 page. Check your serial number in Europe with this Nikon D750 page.
If your camera is in the serial number range known to be affected, you’ll be asked to fill out your contact information and print out both a packing list and a shipping label (Nikon is paying UPS costs in the US). You’ll also be directed to pack your camera in a plastic bag and something other than the original box. Do not include your battery, memory cards, or other accessories.
I should note that my camera was noted as affected, though I’ve not been able to trigger the problem in testing. It appears through a quick and dirty test of the Web page that any camera in the first 30,000 in the US will be determined to be “affected.”