Hi,
I was flashing it using the flash.sh script with jetson-tx2i mmcblk0p1 as the arguments, however the issue has been persistent when flashing this way and with our custom yocto based firmware.
I have since managed to find the issue, after leaving it running overnight at some point it entered cboot and output
cb_vic_scrub: VIC Scrub Failure, error 0x6, cmd = 0x1
over uart.
which led me to this post and this post talking about the DRAM ECC scrub failing if the on UART0_RTS and UART1_TX pins are biased on startup.
I was able to resolve the issue by setting disable_staged_scrub=1; in tegra186-mb1-bct-misc-si-l4t-storm.cfg
If this is likely to cause problems in future please let me know, otherwise thank you for your swift response.