I also have this problem...in first when I tried to flash MAIN it popup some error but then I somehow menaged to flash MAIN just by restarting FAR a few times, but when i try flash FS there is always same error....please help I have trying to debrand my k770i for weeks but no one won't help me...
p.s. FS is K770_R8BC004_FS_S_E_EUROPE_RED53