react-native-calendar-events: Unable to saveEvent() after upgrading version to 1.7.3 from 1.6.1

I used to have a working react-native-calendar-events library at version 1.6.1, but since I upgraded to React Native 60.4 and react-native-calendar-events to version 1.7.3 users cannot add events to calendar.

On Android, they get an error message, on iOS it just crashes the app.

The error message on Android is coming from this asynchronous component helper function:

async function addToCalendar(event) {
  try {
    const startDate =
      Platform.OS === "ios"
        ? format(parse(event.StartDateLocal))
        : parse(event.StartDateLocal);
    const endDate =
      Platform.OS === "ios"
        ? format(parse(event.EndDateLocal))
        : parse(event.EndDateLocal);
    const allEvents = await RNCalendarEvents.fetchAllEvents(startDate, endDate);

    const calendarEvent = allEvents.find(e => e.title === event.Title);
    if (calendarEvent) {
      alert("You have already added this event to your calendar.");
    } else {
      const title = event.Title;

      const {
        Location: {
          AddressLine1: address,
          City: city,
          StateAbbreviation: state,
          PostalCode: zip
        }
      } = event;

      const location = `${address}, ${city}, ${state}, ${zip}`;

      const settings = {
        location,
        startDate,
        endDate
      };
      RNCalendarEvents.saveEvent(title, settings)
        .then(() => {
          alert("Event Saved");
        })
        .catch(() => {
          alert("Error");
        });
    }
  } catch (e) {
    alert("Error");
  }
}

Environment

System:
    OS: macOS High Sierra 10.13.6
    CPU: (8) x64 Intel(R) Core(TM) i7-4770HQ CPU @ 2.20GHz
    Memory: 417.23 MB / 16.00 GB
    Shell: 5.3 - /bin/zsh
  Binaries:
    Node: 10.16.3 - /usr/local/bin/node
    Yarn: 1.10.1 - /usr/local/bin/yarn
    npm: 6.9.0 - /usr/local/bin/npm
    Watchman: 4.7.0 - /usr/local/bin/watchman
  SDKs:
    iOS SDK:
      Platforms: iOS 12.1, macOS 10.14, tvOS 12.1, watchOS 5.1
    Android SDK:
      API Levels: 23, 25, 26, 27, 28
      Build Tools: 23.0.1, 26.0.2, 27.0.3, 28.0.3
      System Images: android-28 | Google Play Intel x86 Atom
  IDEs:
    Android Studio: 3.5 AI-191.8026.42.35.5900203
    Xcode: 10.1/10B61 - /usr/bin/xcodebuild
  npmPackages:
    @react-native-community/cli: 2.9.0 => 2.9.0
    react: 16.8.6 => 16.8.6
    react-native: 0.60.4 => 0.60.4
  npmGlobalPackages:
    react-native-cli: 2.0.1
    react-native-git-upgrade: 0.2.7

I went back to react-native-calendar-events 1.6.1 and I am still getting the same issue.

This library looks like it still uses index.ios.js and index.android.js even though React Native 60+ versions are now on index.js as root. Could this be the problem?

Steps to Reproduce

Please clone: https://github.com/ldco2016/RNapp

What would be a cause of receiving undetermined as a Promise?