Samsung g925i drk repair failed

Operation: Repair DRK
Selected model: SM-G925I
Software version: 26.9

Checking local file… OK
Searching server… OK
Compare local and server file… OK (up to date)
Searching USB Flash interface… COM20 detected
Setup connection… OK
Reading data from phone… OK
Sending data to phone… OK
Sending data to phone… OK
Waiting ADB device… OK
Reading phone info…
Recovery build version: 6.0.1
Boot version: G925IDVU3EPC5
Platform: exynos7420
Boot serial: 05157df53182ba27
Product board: zerolte
Initialization zTool… OK
Running zTool, please wait…
Start… OK
Initialization… OK
Generate and check client proof… OK
Verify proof by client… OK
Checking DRK status… NG!
Writing DRK… error (error(5.6.-14))

IS IT HARDWARE OR SOFTWARE ?????