Bootloader issue on Redmi 9 (MIUI 13.0.2 – Android 12) / Can’t add account for unlock

Hi everyone,
I have a Xiaomi Redmi 9 (M2004J19G) running MIUI Global 13.0.2 (Android 12 SP1A). I want to unlock the bootloader, but I can’t add my Mi Account in the "Mi Unlock status" section. It always shows "Can’t access right now, try again later". It has been 3 days with the same message.

Device info:

Redmi 9 (Lancelot)

Model: M2004J19G

MIUI: 13.0.2 Global Stable (13.0.2.0 SJCMXM)

Android: 12 SP1A.210812.016

RAM: 4 GB

Storage: 64 GB

Baseband: MOLILR12A.R3.MP.B98.1.PE24

Kernel: 1.14.136-PEF

Security patch: 2022年10月01日


Phone background:
The phone was physically damaged when I found it. I replaced battery, screen and the top flex cable.
A technician also installed a clean system to bypass the previous Google account.

Current problems:

The system freezes, apps bug, and multitasking performs very bad.

I want to install an older or different ROM to make it more stable.

But I can’t link my Mi Account to unlock the bootloader.


Questions:

1. Is there any fix for the Mi Unlock account error?


2. Can this happen because the device was flashed before by a technician?


3. Is there any safe method to unlock the bootloader in this situation?


4. What ROM is recommended for Redmi 9 (Lancelot) on Android 12 MI
UI 13 base?



Thanks for any help or suggestions.