Nexus 7 2012 Wifi only version stuck in safe mode, how can I get out of this?

[AC Question]

Nexus 7 2012 Wifi only version stuck in safe mode

Last week my tab went into safe mode and I was not able to bring it back to normal mode.

A. Removed all app except Google.
B. I tried pressing power off and push to safe mode via tab
C. Tried to factory reset twice using tab settings menu
D. Went into recovery mode for cache wipe but volume down was not working and cursor stuck to restart only ..volume buttons works fine when tab is booted.

Nothing worked so decided to flash OS again
A. Used developers.google.com/android/nexus/images to download and flash new image but flash-all failed
B. So used manual commands and using fastboot command removed boot, cache, recovery, system, userdata and flashed again. No result again
C. Then decided to use Nexus 7 root tool kit to flash image but no positive results.

Current state
When tab starts it automatically displays START. If I press then it boots up in safe mode and Wifi & google apps works fine.
If I try to go to recovery options, Google Logo comes and comes back again to START.
If I try restart bottloader then no messages gets displayed and comes back to START screen.

Image I have reloaded was nakasi.

Could you please suggest?