Hi,
Please read the bootloader version string following methods mentioned here:
https://docs.nvidia.com/jetson/archives/r36.3/DeveloperGuide/SD/Bootloader/UpdateAndRedundancy.html#bootloader-version-in-qspi-flash
On a normal 35.5 device, you should get 2295040 with
sudo cat /sys/firmware/efi/esrt/entries/entry0/fw_version
See if modifying it with the correct value makes nvidia-l4t-jetson-orin-nano-qspi-updater work.
I’m not sure if it’s a safe operation so please be careful with it.