Nami Wallet returns witness seen as invalid by Cardano CLI (InvalidWitnessesUTXOW)

[ZDust172]

I am attempting to sign and submit a simple "always succeeds" transaction body built by the CLI and signed with nami wallet.

cardano-cli transaction build-raw \ --alonzo-era \ --fee 200000 \ --tx-in {NAMI_ADDRESS_UTXO} \ --tx-out {SCRIPT_ADDRESS}+1800000 \ --tx-out {NAMI_ADDRESS}+998000000 \ --invalid-hereafter 50000000 \ --protocol-params-file protocol.json \ --out-file tx-script.draft

Signing this file with an initial key in the CLI, I then sign it with nami using
const witnessSet = await window.cardano.signTx(transaction, true);

Generating the following hex CBOR:
a10081825820863d383db3cc7494604d02d3bf214706a18a178ce50eb1f04ad3ef45f50815735840da3ef50001e801bb9580ea361cff86fedef6aab41ebf835dbd246afae02a8b380cbfef0bb1c1ad299b57837dcc04d22a8fc81d713989160513fb14020b7ca203

This hex is sent to the back-end where I do some transformations to get the set in the form of [0, [vkey witnesses]] as shown in #85.

let bufferWitness = Buffer.from(witnessSet, "hex");
let witnessDecoded = await cbor.decodeFirst(bufferWitness);

const newWitness = [0]; // Array format accepted by the CLI
newWitness.push(witnessDecoded.get(0)[0]); // vkey witness generated by Nami
console.log('Result:', cbor.encode(newWitness).toString("hex"));

This generates the following hex CBOR:
8200825820863d383db3cc7494604d02d3bf214706a18a178ce50eb1f04ad3ef45f50815735840da3ef50001e801bb9580ea361cff86fedef6aab41ebf835dbd246afae02a8b380cbfef0bb1c1ad299b57837dcc04d22a8fc81d713989160513fb14020b7ca203

Decoded as:
[0, [h'863D383DB3CC7494604D02D3BF214706A18A178CE50EB1F04AD3EF45F5081573', h'DA3EF50001E801BB9580EA361CFF86FEDEF6AAB41EBF835DBD246AFAE02A8B380CBFEF0BB1C1AD299B57837DCC04D22A8FC81D713989160513FB14020B7CA203']]

When I use cardano-cli assemble to generate the final transaction and submit, I get this error:

ShelleyTxValidationError ShelleyBasedEraAlonzo (ApplyTxError [UtxowFailure (WrappedShelleyEraFailure (InvalidWitnessesUTXOW [VKey (VerKeyEd25519DSIGN "863d383db3cc7494604d02d3bf214706a18a178ce50eb1f04ad3ef45f5081573")]))])

Which I do not understand as the tx body is not altered by the time it is sent to Nami, only signed with a dummy key but I'm assuming that should not affect the witness generated?

Any help would be appreciated, thanks.

*EDIT: I have also attempted loading the transaction through the serialization lib as well and get exactly the same error so it seems like Nami Wallet/serlization lib make different signatures to the CLI, how can this be?

[ZDust172]

Closing as this actually concerns the Serialization lib and is not directly caused by Nami. I'll open an issue there instead.