My Trophy MY22 (3 phase charge, deleted driver camera) has always suffered from inconsistent speed recognition, sometimes whole journeys are made without a single sign being recognised. It does however always work when the infotainment system resets, which is as far as I can work out is random when you power up the car. Having said that if the journey is broken, i.e. the car stopped and locked up then quite often it doesn't recognise any more signs.
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Some of the interesting signs it does pick up when working, like a 70 in a 30 limit, or national speed limit in a 30 would never be able to used as any defence against a speed offence, anyway there is a getout clause about its accuracy of detection.