I had the same issue.
First of all follow this instruction:
http://www.theandroidsoul.com/fix-empty-imei-corrupted-efs-no-sim-unknown-baseband-wifibluetooth-issues-restoring-twrp-backup/
I used terminal from TWRP.
Second update TWRP to latest version. 3.0.2-2 has problem with EFS backup.