Nikon has issued a service advisory for the D810 for noise/bright spots during long exposures and when in 1.2x crop mode.
See the full service advisory below.
We have received a few reports from some users of the Nikon D810 digital SLR camera indicating that noise (bright spots) are sometimes noticeable in long exposures, and in some images captured at an Image area setting of 1.2× (30×20).
After looking into the matter, we have determined that some noise (bright spots) may on occasion be noticeable when shooting long exposures, and in images captured at an Image area setting of 1.2× (30×20).
Nikon service centers will service these cameras that have already been purchased as needed free of charge to the customer. We sincerely apologize for any inconvenience this issue may have caused.
Identifying affected products
To check whether or not your camera is one of those affected by this issue, please click the Affected Product Serial Numbers link below and enter your D810’s serial number as instructed. Your camera’s serial number will be checked against those of affected products. If your camera is one of those affected, you will be forwarded to additional instructions. If your camera is not one of those affected, you may continue using your camera without concern for this issue.
You can check your D810 serial number here on Nikon’s website to see if it is affected.