GT-3520I FLASH Failed

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Platform: Samsung Spreadtrum
Selected port: COM6
Selected model: GT-C3520I
Selected port: USB
To connect GT-C3520I phone perform the following steps:
1. Disconnect phone battery.
2. Press and hold "1" button, connect USB cable.
3. Connect battery.
Connecting…
Phone found.
Sending preloader…
Preloader send successfully
Sending mainloader…
Mainloader send successfully
Firmware write started.
Writing BOOT section…
BOOT section has been written successfully.
Writing User section…
User section has been written successfully.
Writing Res section…
Writing Firmware Failed

help step by step….octopus team
thx