Team Calendar subscription does not work in Google Calendar, but does in Apple Mac Calendar and Outlook

Summary

Attempting to subscribe to Team Calendar link in Google Calendar returns error:
"Settings Error - We could not parse the calendar at the url requested."

Subscribing to the same url in other clients Apple Calendar and Outlook works without error.

Environment

• Team Calendar v. 5.3.19, 5.3.20

Steps to Reproduce

1. Following the steps to generate the calendar subscription url in Confluence calendar . . . > Subscribe
2. Then in Google Calendar, attempt to add the calendar by subscription url (see: Subscribe to and from Team Calendars)
3. Google Calendar appears to begin to start but then displays the error.  

Expected Results

Calendar subscription should be added successfully

Actual Results

Google displays the error.

"Settings Error
We could not parse the calendar at the url requested."

UPDATE: In recent Google Calendar design update, it looks like no error is displayed but no success message is reported and no calendar items are imported on the calendar.

UPDATE: We have also found that office365 calendars experience the same issues. The calendar can be added with no error message, but no calendar items are imported on the calendar.

Notes

In trying to investigate the source of the error, I've downloaded the .ics files and tried checking them for errors with some online ICS file format validator which gave errors on the VTIMEZONE data. For troubleshooting, we asked the customer to try alternative timezones as they also ran into other issues with the "Hong Kong" timezone in other another bug (CONFSERVER-48595 / -CONFSERVER-48981-) but they still experienced the errors on both of their calendars.

As additional troubleshooting, I downloaded the .ics files from the calendar subscription urls and tried instead to just import them and received similar errors. If I manually edited the ICS files to remove the whole VTIMEZONE content, I was able to import the calendar data into a temp calendar for testing. I tried just removing only bits of the VTIMEZONE data but still ran into issues until I removed everything in between and including:

BEGIN:VTIMEZONE
END:VTIMEZONE

Workaround

There is no known workaround currently available for Google Calendars.

Subscribing still seems to work with other Calendar applications such as Microsoft Outlook, Apple Mac Calendar, and Apple iOS Calendar.