Blue screen and reboot

Hi

I have an iPhone 6. With a blue screen rebooting without stopping , it doesn't start at all, after the apple logo , comes this blue screen with a black spot colored as the apple logo goes away, a blue screen and a black spots forming a non explained image like cloud, but I get the iTunes logo clearly as I put it on DFU mode, which made believe is not a graphic issue, when I connect it to iTunes error 1671 appears, not able to restore. the person says that he drops it down, so I thing it couldn't be a board damage, for I looked on the board everything seems to be fine , I even took out all the screws to make sure it is not a wrong screw in a wrong place, actually the phone never been disassembled before, so it's not that the reason. What it could be the problem then?

Please help

Thank you