PS4 slim suddenly having booting issues after update

Hi Everyone.

About a week ago, I updated my PS4 Slim to version 11.50. After that I have seen strange problems coming up. The PS4 wont boot up for long time, and then one screen shows up with below message:

Connect a USB storage device that contains an update file for reinstallation for version 11.50 or later. You can download the update file for reinstallation from playstation.com.

After pressing on Cancel, PS4 starts up and I am able to play games. But this process takes a long time.

Fixes I tried:

1. Checked more updates. None present.
2. Booted in Safe Mode and selected Rebuild Database.
3. Initialized the PS4. (lost all game updates and option files).

But after restart, I played a game and did not use it for sometime. After that when I pressed the PS button on my controller, the power button blinked sometime and it shut off.

Power saving settings: Turn off after 20 minutes.

Now when I restarted again, I am seeing the message that "PS4 was not properly shut off and it restarted again" just as if you suddenly switched it off and restarted.

What's happening with my beloved PS4? Power Savings Settings should have ensured it should have had a graceful shutdown, right?

Thanks