Jetson Jetpack 4.5.1 endless reboot

After using SDK Manager (latest) to flash OS to AGX-1 the AGX-1 is now stuck in endless reboot showing nVidia splash screen, and then black, and then nVidia splash screen.

I expected SDK manager to reset everything, but it appears that the boot sequence is wrong. I had previously flash JP4.4.1 and modified boot to use sda1 rather than mmcblkp01 for the /dev/sda1 (see below).

sed -i -e "s/mmcblk0p1/sda1/" /mnt/boot/extlinux/extlinux.conf

Is there a special mechanism for full factory reset on AGX-1 prior to use of SDK Manager? I have been unplugging AGX-1 and then pressing center button and holding and pressing left button (front); successful in recovery mode and USB connection to Ubuntu18.04 VM on macOS11.2.3 using VirtualBox (latest).

I also tried flashing uSD card with JetPack 4.5.1 uSD card image for Xavier NX; it worked in the same fashion, i.e. endless reboot w/ nVidia splash screens.

Device also has 500 GB nVME in M2 slot; 1 TB SSD connected via USB3 cable.

IDK; reflashed MMC w/o uSD card. All good now.

Is your issue on AGX or on NX?

When you see those errors on AGX, do you also have M2 card and SSD connected at that case?