Here's the guide of how to flash stock firmware with OST LA 6.0.4.
Prerequisite: Your phone has bootloader unlocked, check this guide if you haven't:
You must use OST LA provided by heineken78 , which provided in the bootloader unlock topic.
(Right click on the setup.bat and run with administrator privileges)
1. Download the firmware provided by blackpanther0582.
Skip step 2 to 5 If you're flashing Nougat stock firmware.
3. Use a text editor that supports Unix formats (e.g. Notepad++) to open the file with mlf extension.
4. Modify these values as shown below and save:
INITOPTION = 0x20000 INITDLTYPE = 0x60 SECURITY_VER = 0x0001
6. Check "Normal Download", "Clear user data", and UNCHECK "Check System AP status".
7. Put your phone to download mode by connecting your phone to PC when powered off, then click next.
8. You might see a prompt to tell you "Ask customer to try to unlock it first", it's for service point employees. Just ignore that and click Yes.
9. After firmware flashed, you might see an error with code 0xC6DA. Ignore that, close the OST LA and force reboot your phone by press and hold Power button for few seconds.
That means the phone flashing result can't be sent to FIH server.
@heineken78 for providing unpacker and patch
@blackpanther0582 for providing stock firmware