I've never had a problem with the accuracy of my Nano VNA but it can be a frustrating POS when you need to test somethign quickly. I just noticed the marker was at 462.7MHz and this duplexer was tuned for 462.6MHz, so the notch appears to be in about the right spot. The uncal connected through trace on the Nano thing was about -2.9dB so the marker at -79.45dB for one of the duplexer notches is in the ball park. This duplexer was previously tuned with an HP/Agilent spectrum analyzer with tracking generator and it tuned up nice and fast with about 75 to 76dB notches and low insertion loss. These things were apparently designed to be used by very small people with excellent eyesight and lots of time on their hands. Not to mention needing strong reading glasses to see the display and the push buttons will kill your fingers after awhile or your fingers might be too fat to use the touch screen feature.

To tune something you would have to make a small adjustment then wait for the slow sweep then find you went too far then adjust again and wait and oops too far the other way and keep doing that until you go lucky. In my humble opinion I think its probably ok for rough testing a duplexer but with its 1 second sweep time it would push me over the edge trying to tune something and I would smash it. I came close to just smashing the VNA with a hammer and tossing it. I just spent a frustrating 30min with my Nano VNA trying to get it calibrated and gave up and did an uncalibrated sweep of one notch on a flat pack 6 cavity notch duplexer.

Nanovna v2 plus4