Completed building my K3S (2.7kHz stock filter only, KP3A 100 W PA). Carried out 5 W and 50 W calibration successfully. Subsequently upgraded Software successfully. Shut down but next day noticed power out was low. Re-run Calibration but now it fails even on 5 W showing "ERR TXGN". I'd appreciate any help. Regards. Jim EI4HH.