Hi people, maybe its old new but oh well, might help someone one day.
Just to let you for all Nx 200t 2015 owners that updating your nav from sock firmware using the usb key method or Enform Over the Air that they is a very high probable chance you might brick your NAV upon next bootup for the upgrade process (known glitch but undocumented by lexus).

The display was stuck on the Nav Warning screen and no matter how I restared the car , it did not solve the problem.

I solved this crappy sofware bug by unplugging the negative of my battery terminal for 30 sec and plugging it back and voila, upgrade finished correctly.

Here is the crappy software link: https://securedp.lexus.com/download-app/getUpdates


I updated the sw because I have many freezes and slow down ...
Please make sure to tighten the screw back on the battery correctly as you could die not doing so.

Good luck!

Well hope this help you out.