hi help i have this problem ((recovery ... File: \EFI\Microsoft\Boot\BCD. Error code: 0xc0000034 lumia 1020 )) after i update into Windows 10 Mobile build 10166
If not try using the lumia software recovery software. Or windows phone recovery software, to 'reflash' the software on your phone.
Note: with that recovery software you will go back to windows 8.1, so you need to do the upgrade to win 10 again if you want to test the build.