hello roryb,
it’s mentioned by developer guide, Secure Boot.
after the SecurityMode (also known as odm_production_mode) fuse is burned with a value of 0x1, all additional fuse write requests will be blocked.
we’ve tested and it’s confirmed we can burn fuses and boot up success on Orin-NX-8GB + r35.4.1
you may see-also Topic 263458 for reference.