I am getting full speed after factory reset as mentioned earlier, only issue remaining is router shows wrong result in the inbuilt SPEEDTEST (same result via mobile app, website via wifi or even...

I have a 40Mbps U/D fibre line. Until 1st of March 2023, the router's internal SPEEDTEST used to show the correct speed (~40Mbps U/D) during the test and also had a guaranteed bandwidth of ~40Mbps...