Hikvision NVR can't save (most) settings, PnP doesn't work and other weird things

Hello,

I have DS-7608NI-I2 / 8P which is now around 4 years old and just recently some weird things has started happening:

- I can upgrade firmware. Done just that today - I'm now running V4.40.016 build 200803 which is the latest at the time of writing this post
- I can save some settings (for example I can enable SSH but reboot kills it and removes that tick box, can't remember if that's normal)

Now, here is the (very) problematic part:

- I can't save most of the settings - message...

Hikvision NVR can't save (most) settings, PnP doesn't work and other weird things