[Shield Tablet Q&A, Help & Troubleshooting] e-stimuli:
Hello,

I was in a similar situation but finally managed to fix this boot issue on my K1.

What I have, Nvidia Shield Tablet K1

What I did wrong, flashed via fastboot a stock ROM image from Nvidia GameWorks - SHIELD Open Source Resources and Drivers

But not the correct one for Shield K1

I had the following steps for this recovery ROM (not for K1 tablet...):

fastboot flash recovery recovery.img

fastboot flash boot boot.img

fastboot flash system system.img

fastboot flash userdata userdata.img

fastboot flash dtb tegra124-tn8-p1761-1270-a04-e-battery.dtb

fastboot reboot

Flashing them failed on userdata (not enough space) and results in K1 to be stuck on boot and the Nvidia logo for ages.

(For a K1 tablet, you don't have a userdata and dtb flash image steps). I think what messed up my K1 is the dtb flashing step because formating, erasing and flashing recovery, boot, system and userdata partitions didn't have any effects on being stuck at boot.

What I did to get out of this mess and what you need:

Stock ROM K1: nv-recovery-image-shield-tablet-k1-factory0_0_0

fastboot + adb

twrp for K1 for revovery partitions

And know your K1 partitions

Via adb shell:

cd /etc

cat recovery.fstab

shieldtablet:/etc # cd /etc

shieldtablet:/etc # cat recovery.fstab

Result:

/dev/block/platform/sdhci-tegra.3/by-name/APP /system ext4 ro wait

/dev/block/platform/sdhci-tegra.3/by-name/CAC /cache ext4 noatime,nosuid,nodev,data=writeback,nodelalloc wait,formatable

/dev/block/platform/sdhci-tegra.3/by-name/LNX /boot emmc defaults defaults

/dev/block/platform/sdhci-tegra.3/by-name/MSC /misc emmc defaults defaults

/dev/block/platform/sdhci-tegra.3/by-name/UDA /data ext4 noatime,nosuid,nodev,data=writeback,noauto_da_alloc wait,check,formatable,encryptable=/dev/block/platform/sdhci-tegra.3/by-name/MDA

/dev/block/platform/sdhci-tegra.3/by-name/RP3 /usercalib ext4 noatime,data=writeback wait,formatable

/dev/block/platform/sdhci-tegra.3/by-name/USP /staging emmc defaults defaults

/dev/block/platform/sdhci-tegra.3/by-name/MDA /metadata emmc defaults defaults

/dev/block/platform/sdhci-tegra.3/by-name/SOS /recovery emmc defaults defaults

/devices/platform/sdhci-tegra.2/mmc_host* auto vfat defaults voldmanaged=sdcard1:auto,encryptable=userdata

/devices/tegra-ehci.0/usb* auto vfat defaults voldmanaged=usb:auto

/dev/block/platform/sdhci-tegra.2/by-num/p1 /sdcard vfat defaults recoveryonly

Via adb shell:

cd dev/block/platform/sdhci-tegra.3/by-name/

ls -al

Resust:

shieldtablet:/dev/block/platform/sdhci-tegra.3/by-name # ls -al

total 0

__bionic_open_tzdata: couldn't find any tzdata when looking for GMT!

drwxr-xr-x 2 root root 520 2019-11-19 08:27 .

drwxr-xr-x 4 root root 600 2019-11-19 08:27 ..

lrwxrwxrwx 1 root root 21 2019-11-19 08:27 APP -> /dev/block/mmcblk0p13

lrwxrwxrwx 1 root root 21 2019-11-19 08:27 CAC -> /dev/block/mmcblk0p14

lrwxrwxrwx 1 root root 21 2019-11-19 08:27 CHG -> /dev/block/mmcblk0p20

lrwxrwxrwx 1 root root 21 2019-11-19 08:27 DTB -> /dev/block/mmcblk0p11

lrwxrwxrwx 1 root root 20 2019-11-19 08:27 EKS -> /dev/block/mmcblk0p2

lrwxrwxrwx 1 root root 20 2019-11-19 08:27 FB -> /dev/block/mmcblk0p3

lrwxrwxrwx 1 root root 21 2019-11-19 08:27 FBP -> /dev/block/mmcblk0p21

lrwxrwxrwx 1 root root 21 2019-11-19 08:27 FCG -> /dev/block/mmcblk0p22

lrwxrwxrwx 1 root root 21 2019-11-19 08:27 FCT -> /dev/block/mmcblk0p18

lrwxrwxrwx 1 root root 21 2019-11-19 08:27 GPT -> /dev/block/mmcblk0p24

lrwxrwxrwx 1 root root 21 2019-11-19 08:27 LBP -> /dev/block/mmcblk0p19

lrwxrwxrwx 1 root root 21 2019-11-19 08:27 LNX -> /dev/block/mmcblk0p12

lrwxrwxrwx 1 root root 21 2019-11-19 08:27 MDA -> /dev/block/mmcblk0p17

lrwxrwxrwx 1 root root 21 2019-11-19 08:27 MSC -> /dev/block/mmcblk0p15

lrwxrwxrwx 1 root root 20 2019-11-19 08:27 NCT -> /dev/block/mmcblk0p4

lrwxrwxrwx 1 root root 20 2019-11-19 08:27 RP1 -> /dev/block/mmcblk0p6

lrwxrwxrwx 1 root root 20 2019-11-19 08:27 RP2 -> /dev/block/mmcblk0p7

lrwxrwxrwx 1 root root 20 2019-11-19 08:27 RP3 -> /dev/block/mmcblk0p8

lrwxrwxrwx 1 root root 20 2019-11-19 08:27 RP4 -> /dev/block/mmcblk0p9

lrwxrwxrwx 1 root root 21 2019-11-19 08:27 SOS -> /dev/block/mmcblk0p10

lrwxrwxrwx 1 root root 20 2019-11-19 08:27 TOS -> /dev/block/mmcblk0p1

lrwxrwxrwx 1 root root 21 2019-11-19 08:27 UDA -> /dev/block/mmcblk0p23

lrwxrwxrwx 1 root root 21 2019-11-19 08:27 USP -> /dev/block/mmcblk0p16

lrwxrwxrwx 1 root root 20 2019-11-19 08:27 WB0 -> /dev/block/mmcblk0p5

MAP boot, system, blob (staging) partitions with corresponding memory block

Ex: boot -> LNX -> /dev/block/mmcblk0p12

Via adb shell and using the images from K1 ROM nv-recovery-image-shield-tablet-k1-factory0_0_0 (check if your tablet k1 has the same partitions)

dd if=boot.img of=/dev/block/mmcblk0p12

dd if=system.img of=/dev/block/mmcblk0p13

dd if=blob of=/dev/block/mmcblk0p16

By getting from another ROM: tegra124-tn8-p1761-1270-a04-e-battery.dtb (renamed tegra124.dtb)

dd if=tegra124.dtb of=/dev/block/mmcblk0p11

Still failing... and stuck at boot so I decided to restore nv-recovery-image-shield-tablet-k1-factory0_0_0 via fastboot a last time but cleaned everything first:

twrp wipe all system cache data

then

fastboot flash system

fastboot erase boot

fastboot flash boot

fastboot erase staging

fastboot flash staging blob

fastboot reboot

And my Shield Tablet K1 was working again!! And very happy to have my Nvidia Shield K1 back (with latest LineageOS 15.1 ROM and working like a charm)!

I did a lot of stock ROM erase / format / restore on these partitions before and they all failed before. But I thing here the main difference is around the DTB partition.

May be the dd if=tegra124.dtb of=/dev/block/mmcblk0p11 step did properly restore the dtb info and partition or actually "corrupt" it in a way that cause the K1 to properly boot back. I don't know.

Hope that can help someone in the same situation!