Does it randomly reset roughly every 30mins?
If so it’s a known problem with no known solution that I am aware of, and I have been searching for a while now.
I see a lot of people complaining about there ng4 unit failing lately. I guess they are coming to their end of life now after 8 or so years. It’s a shame as it takes up a big part of the car and there is no replacement that can use the flip up screen, unless you buy the same unit of course at a cost of £2k!!!