I also had problems measuring SWR and reflected power. Even when setting the minimum output power, it showed 0.3W reflected. And did not change the value when the output increased. The converter ADC78H90CIMT (U17) did not work properly. Chip heating 92°C(197.6°F). Although FWD displayed correctly. R...
Have you checked the signals coming to ADC78H90CIMT (U17) FWD PWR and REW PWR (J15)? After establishing the presence of adequate voltage levels, it will be clear whether this is a hardware or software problem ....