I don't know what triggered the issue i was roaming around some apps suddenly the main menu was not responsive only the nav bar was working everything on the main menu didn't work had to restart the device.
I had issues when unlocking the phone using pin. black screen which got locked after timeout. to get device usable I unlocked via iris. this time status bar was visible. I swiped Down to open notification shade, and home screen was usable. It happend couple of times, I restarted phone and never saw it till date.