ERROR: Endless Looped Duplication of Appointments in Google Calendar

[sapanjs]

I have setup the script to sync 2 calendars as such:
var sourceCalendars = [ // The ics/ical urls that you want to get events from along with their target calendars (list a new row for each mapping of ICS url to Google Calendar)
// For instance: ["https://p24-calendars.icloud.com/holidays/us_en.ics", "US Holidays"]
// Or with colors following mapping https://developers.google.com/apps-script/reference/calendar/event-color,
// for instance: ["https://p24-calendars.icloud.com/holidays/us_en.ics", "US Holidays", "11"]
["https://na02.patientnow.com/Services/SyncSchedule.aspx?sync=5367DC13-9556-4C8A-B66C-B0DEBCE95229.ics", "SJ's PatientNOW"],
["https://na02.patientnow.com/Services/SyncSchedule.aspx?sync=B0589A56-48E1-424D-8DCC-4C7EFFBB1FA0.ics","Kat's PatientNOW"]

];

What is happening is that the first calendar (GREEN) is syncing fine, but the second calendar (PURPLE) keeps doing this:

The execution log is showing error as such: (when I delete the calendar completely, and let the software recreate - it starts working for a little bit of time, but then it does the duplication again).
Jan 28, 2025, 11:53:02 AM Error API call to calendar.events.insert failed with error: Backend Error
at callWithBackoff(Helpers:1290:9)
at processEvent(Helpers:624:20)
at unknown function
at startSync(Code:218:15)

[sapanjs]

Here is an error screenshot:

[sapanjs]

@derekantrican Any thoughts here?

[Lonestarjeepin]

Sounds like you have non-persistent event IDs in your second calendar. - Check out the patch in #283. I've seen the delete API error before when I've overwhelmed Google and deleted a bunch of events. It should resolve in a few days after you fix the underlying issue.