If you experience an issue where the NVR will not save changes made within the menus, the first test will be to down power the NVR and disconnect the HDD cables to all installed HDD’s and re-apply power to the NVR.
Make some test changes in the NVR’s menu and save them.
Exit the menu and re-enter the menu and confirm the settings have been saved.
Re-attach the HDD’s one at a time and power up the NVR. Make further test changes in the menu and confirm they have saved.
It is suspected that 1 HDD installed within the NVR may be the cause of the issue.