Another workaround if you see the bash (initrd) console in UART after running OTA upgrade.
1. reboot the device 7 times,
2. the device should be able to boot up properly.
3. edit the /boot/extlinux/extlinux.conf to do following changes:
- APPEND ${cbootargs} quiet
+ APPEND ${cbootargs} root=/dev/mmcblk0p1 rw rootwait rootfstype=ext4 console=ttyTCU0,115200n8 console=tty0 fbcon=map:0 net.ifnames=0
4. Reboot the device, and run "dpkg-reconfigure nvidia-l4t-bootloader"
5. reboot device.