Ember-cli acceptance test times out on await click(); qunit error: Uncaught (in promise) Error: pushFailure()

I'm trying to create an acceptance test for the login page of a webapp. Everything is almost working, except the await click(element) promise never resolves:

import { module, test } from 'qunit';
import { visit, currentURL, fillIn, click, waitFor, getSettledState } from '@ember/test-helpers';
import { setupApplicationTest } from 'ember-qunit';
import { invalidateSession } from 'ember-simple-auth/test-support';
import { setupMirage } from 'ember-cli-mirage/test-support';

module('Acceptance | login', function(hooks) {
  setupApplicationTest(hooks);
  setupMirage(hooks);

  test('login page | login success', async function(assert) {
    assert.timeout(5000);

    console.log('start', getSettledState());

    await visit('/login');
    assert.equal(currentURL(), '/login');

    await waitFor('.btn-primary:disabled');

    await fillIn('input[type="text"]', 'mirage');
    await fillIn('input[type="password"]', 'password1234');

    await waitFor('.btn-primary:not([disabled])', 2000);
    console.log('btn enabled');

    let btnSubmit = document.querySelector('.btn-primary');
    assert.equal(btnSubmit.disabled, false);

    await click(btnSubmit);
    console.log('await btn click');

    await waitFor('.nav-tabs', 4000);
    console.log('nav complete');

    assert.equal(currentURL(), '/bid-search/planetbids-bids');
    console.log('finished', getSettledState());
  });
});

If I run this test as-is, "await btn click" doesn't log in the console, until it times-out. I also get the qunit error "Uncaught (in promise) Error: pushFailure() assertion outside test context, in ___ at internalStart" (underscores added by me)

HOWEVER, if I remove the await part of the click(btnSubmit) call, the test completes successfully BUT, the last check of getSettledState() returns this:

hasPendingRequests: true
hasPendingTimers: true
hasPendingWaiters: false
hasRunLoop: true
pendingRequestCount: 1

So it looks like if I run the test correctly with await click(btnSubmit), the test times out on the click(), but if I just call click(btnSubmit), the tests complete successfully, although testem or qunit doesn't know all the tests completed. What am I doing wrong?