My Nikon D750 recently started acting strange in the following ways: would not take pictures in raw even though raw+jpeg selected, taking a picture would save to card but replace the oldest picture on the card, the mirror would go into lockup even though was shooting through the viewfinder and require a second press on the release, and finally got the dreaded "err" flashing.
Removed the battery, cards, and lens for 24 hours, then was able to take 5 pictures. Tried to access the menu functions, and the camera would not save any changes. Tried different batteries, cards, lenses and finally saw that a firmware update was posted in January. Downloaded the file on a freshly formatted card, and tried to update, the camera showed the update process proceeding until the end when it flashed "update failed, contact Nikon Customer Service". The camera will not function now except to turn on. Pressing any button has no effect, pressing the shutter release button sounds like the mirror moves into the lockup position, pressing the button again the camera goes into flashing err.
Finally my question: is there anyway to force a reboot of the software running the camera? Even if I get the camera running again to try a second firmware update, will it matter? Is the camera DOA?
The service center is shutdown until the covid-19 restrictions are lifted, at which time I'm sure there will be a surge in repair requests. I have already had the shutter repaired when it failed in the first year under warranty, this shutter has 2556 shots on it. Considering another camera if this one turns into a once per year return to Nikon.
Longtime Nikon user, 40+ years