okat lemme just be specific, I have been trying to fix Itel prime 4 that hang at Itel Logo, like other itels A series e.g A11,A12. for Itel A series I used Factory Spd upgrade tool with spd upgrade tool 0001. but for prime 4 I tried so many tool with different firmwares but I got the same error 'UART sent fail ' whenever I started the flashing.