Sometimes, the persist file alone isn’t enough. Download the MIUI 12.0.3.0 Fastboot ROM (Global) and flash it completely using Mi Flash Tool (select "Clean All" – never "Clean All and Lock" if you use custom ROMs).
The persist partition stores Bluetooth/Wi-Fi calibration data. Corruption is the #1 reason for "extra quality" loss. redmi note 5 pro wifi fix file extra quality
If you have flashed the stock ROM and the Wi-Fi turns on but the signal is weak, you may need to inspect the hardware. Sometimes, the persist file alone isn’t enough