Idea...
Try the "Memloader Test" as I call it.
See if the Minerva Training Cell can work.
Send Memloader... See if it fails or not.
Will give you an idea of whats working and what isn`t. Make sure you use latest memloader with Minerva.
If it fails: With 246400 bytes
I`ve had a few consoles with this fault. It seems to be a hard fault between the Tegra and the RAM.
MAX77620 are functional, fuel gauge, bq, m92, all mosfets are fully working. Ref. Oscillator crystal working... Hekate boots... Correctly built and rebuilt eMMC, I thought "cracked ball under RAM". Reflowed. Nothing. Even reballed a RAM chip(without a jig. Took hours.)
It may be related. Or you may be lucky in that its a cracked joint.
If you can get BIS key 0 and PRODINFO is intact, you can build emmc from scratch, with fresh keyblobs if need be.
Just trying to give a few pointers.
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As Jdbye says, you can indeed remove certs and recalc hashes in PRODINFO, but you will struggle with the Device Cert(ecc-b233) if its missing. Offset 0x480 if I remember correctly