Do you know if i can just flash 5.1 ROW LTE without changing anything?
If you have the us lte ota.zip file you should be able to just replace the system image files and boot.img files in the zip file like i did to roll back to an older Android 7.0 build.
If you were on 5.3, then you may have been on ROW Lte as i am not sure if the Usa Lte 5.3 had come out yet.
The steps i did were.
1. Apply the latest twrp 3.2.0 for the Nvidia shield tablet, also keep a copy on internal memory or sd card to reflash afterwards (.img file)
Make a twrp full backup of your working 5.3 if you want an easy way to roll back. You should be able to flash the 5.3 ota again to get the device booting again, and then you can make a twrp backup if you want.
2. Copy Shield Tablet 5.2 zip file to internal memory or sdcard along with no more ota zip
(not the official nvidia ota, as because of the blob files twrp will complain that it's an older firmware and you can't flash it, maybe if you flashed the 5.1 blob files from the Android development thread that has the 5.1 row lte zip it might allow you to flash the official 5.2 ota from nvidia as it will consider that it is newer)
3. Wipe system, data, davlik and cache (but not internal memory or sdcard
4. Flash the 5.2 row lte.zip (5.2 wifi should also work if you have a wifi model and want to roll back)
5. Flash the nomoreota.zip to remove the danger for the pyro tab from being bricked, also this would stop you from being notified of the 5.3 update from Nvidia if you don't want it (this can be found in the st-yy battery thread)
6. Reflash twrp just in case rom updated recovery to stock
Then reboot the device.
That's how i rolled back