Error uploading one-time keys TypeError: account.unpublished_fallback_key is not a function

Describe the bug
A undocumented error called Error uploading one-time keys TypeError: account.unpublished_fallback_key is not a function is printed in the console, when using loginWithPassword or using an access token to login.

To Reproduce
Steps to reproduce the behavior:

1. Setup matrix-js-sdk for Encryption
2. Try to login via password and username

this.client.loginWithPassword(username, password, (err, res) => {
    this.client.initCrypto().then(() => {
        this.client.startClient({});
    })
});

logger.js:57 Error uploading one-time keys TypeError: account.unpublished_fallback_key is not a function
    at http://localhost:4200/vendor.js:61196:39
    at http://localhost:4200/vendor.js:60952:9
    at LocalStorageCryptoStore.getAccount (http://localhost:4200/vendor.js:74620:5)
    at OlmDevice.getAccount (http://localhost:4200/vendor.js:60947:22)
    at http://localhost:4200/vendor.js:61195:16
    at LocalStorageCryptoStore.doTxn (http://localhost:4200/vendor.js:74646:28)
    at http://localhost:4200/vendor.js:61194:32
    at Generator.next (<anonymous>)
    at asyncGeneratorStep (http://localhost:4200/vendor.js:107143:24)
    at _next (http://localhost:4200/vendor.js:107165:9)

Expected behavior
I would expect the encryption to work and be better documented? It's not clear how I could add/generate key according to the implementation guide (https://matrix.org/docs/guides/end-to-end-encryption-implementation-guide) after logging in, similar to the element client, where you can import keys after logging in.

The example in the repository doesn't address this issue:
https://github.com/matrix-org/matrix-js-sdk/blob/develop/examples/crypto-browser/olm-device-export-import.js

Desktop (please complete the following information):

• OS: Mac OS
• Browser Chrome
• Version 96.0.4664.110

Start by reproducing the reported loginWithPassword/initCrypto flow and compare it with examples/crypto-browser/olm-device-export-import.js and the linked end-to-end encryption implementation guide. Trace the account lookup shown in the stack trace to determine why unpublished_fallback_key is unavailable. Done means encryption initialization no longer logs the TypeError and the required key generation or import flow is documented.