I used a NOX for the first time a couple of days ago, and the previous owner said it was updated to the latest version, and I experienced the same issue. Every target, including surface clad, showed max depth.
I posted on another forum and they said, -- oh you don't need the depth meter, just go by tone or sound or somesuch. I'm sorry, but when I buy a product, I want all of its features to work as expected.
That attitude is sort of like buying a car with a stick shift, and the clutch doesn't work, and people say -- oh you don't need a clutch, just shift by ear and by feel of the gear ratio. Yes, you can drive a stick this way without a clutch, but I'd rather have a working clutch.
I hope there is a fix for this. When I use a machine, I use every piece of information it gives me, not just sound. For me, it looks like the Nox may end up being an expensive door stop, as I do quite fine with the E-Trac.