After a complaint filed by a certain number of Nikon D750 users, who stated that some D750 units had experienced odd flare patterns when bright light sources were located just outside the frame when shooting, Nikon released another statement, this time with precise instructions on how the D750 owners should solve the current problem on their own.
In today's statement issued by Nikon, it has been said that this issue occurs only with models featuring a particular serial number, and that owners can check the serial number of their camera on Nikon's official website. If your camera belongs to the group of those problematic, you will be supplied with additional instructions. However, some models whose serial number suggests that they are affected by the said flare problem may have already been repaired, which is indicated by a black dot inside the tripod socket (as in the picture below).
Earlier this month, the company Nikon already announced that this problem indeed arose with some Nikon D750 bodies, especially when the source of light was at a very narrow range of angles in relation to the camera when shooting. In this situation, the flare occurs in the upper part of the photograph, with a shadow in the shape of a dark band across the top of the frame, which blocks the subject of the image. Research revealed that internal reflections within the AF module at the bottom of DSLR bodies were the principal reason for the development of such a situation.
Nikon's statement in relation to this issue can be found on the official website of the company.