Uncaught (in promise) TypeError: envelope.switch is not a function

[mliu]

I'm seeing this error when trying to sign and submit my transaction with Freighter:

Uncaught (in promise) TypeError: envelope.switch is not a function
    at Function.fromXDR (transaction_builder.js:844:1)
    at _callee2$ (assembled_transaction.js:723:1)
    at tryCatch (assembled_transaction.js:251:1)
    at Generator.<anonymous> (assembled_transaction.js:339:1)
    at Generator.next (assembled_transaction.js:280:1)
    at asyncGeneratorStep (assembled_transaction.js:536:1)
    at _next (assembled_transaction.js:550:1)

I'm using the following dependencies:
"@stellar/stellar-sdk": "12.3.0"
"@stellar/freighter-api": "3.0.0"
"@huma-finance/soroban-tranche-vault": "0.0.15" (our client generated from soroban bindings)

Here's my relevant code to reproduce:

import { signTransaction } from '@stellar/freighter-api'
import { Client as TrancheVaultClient } from '@huma-finance/soroban-tranche-vault'
const trancheVaultClient = new TrancheVaultClient({
  publicKey: 'GDLSHY22H7KOU3V3B2GTSYWYZY6YRDNJTSQAGUK7XPHJAFIVPKPDFKH4',
  networkPassphrase: 'Test SDF Network ; September 2015',
  contractId: 'CB6K4IUC3CJHIWVHHLBDTGXVS6CT64EKGD5CGBIDNMSAKVZHCWQ3LM2D',
  rpcUrl: 'https://soroban-testnet.stellar.org',
  signTransaction,
})
const tx = await trancheVaultClient.deposit({
  lender: 'GDLSHY22H7KOU3V3B2GTSYWYZY6YRDNJTSQAGUK7XPHJAFIVPKPDFKH4',
  assets: 100000000,
})
console.log(tx)
const txSigned = await tx.signAndSend()
console.log(txSigned)

When I copy the XDR of the transaction and sign it in the Stellar Lab, it works just fine. Does anyone know how to fix this?