A: Usually, Widevine drops from L1 to L3 (no HD playback) because the keystore is wiped. No fix.
This leads to one of the most searched tech modifications: .
If you want to avoid the high risk of bricking your device, you can make a Chinese ROM function almost identically to a Global one:
on a computer to uninstall pre-installed Chinese apps that the phone won't let you delete normally. Switch Keyboards:
After converting your Oppo A5 to a global ROM: