Great call ruling out general code issues first—with 98% of your 3000 calendar integrations working smoothly, the problem is almost certainly tied to specific settings on those 50 tricky accounts. Let’s break down the most likely causes and how to check them:

• Calendar-specific permission locks
  Some calendar owners might have tweaked sharing settings to block external apps from deleting events. Even if your app has access to the calendar, the owner could’ve set your app’s permission level to "View only" or "Edit events but can’t delete". To confirm, have the owner (or you, if you have access) check the calendar’s sharing settings in the Google Calendar web app—look for your app’s service account or connected user in the permissions list and verify the access level.

• Google Workspace domain admin restrictions
  If those 50 accounts are part of the same Workspace domain, the admin might have put API restrictions in place that block event deletion for third-party apps. Common limits include:

  • Disabling the Calendar API for specific organizational units
  • Using narrow OAuth scopes that don’t include deletion rights (like https://www.googleapis.com/auth/calendar.events.readonly instead of the full https://www.googleapis.com/auth/calendar.events)
    Reach out to the domain admin to ask if any such policies are targeting those accounts.

• Event ownership conflicts
  Your app might be trying to delete events it didn’t create. Google Calendar only lets the event owner or users with full edit permissions delete events. If the event was added directly by the calendar owner (not through your app), your app won’t have the rights to remove it. Use the API to pull the creator field of the problematic events to confirm who made them.

• Quota or rate limit hits (less likely, but worth checking)
  While 403 errors from rate limits usually come with a rateLimitExceeded reason, it’s not impossible. Check if those 50 accounts have used up their daily Calendar API quota. You can view quota usage in your Google Cloud Console under your project’s API metrics.

• Service account impersonation issues
  If you’re using a service account to access these calendars, make sure impersonation is properly set up for each of the 50 accounts. Sometimes domain admins revoke a service account’s ability to impersonate specific users, which would trigger this forbidden error.

A quick debugging tip: Pick one of the problematic accounts, log into Google Calendar web with the same credentials your app uses, and try deleting the event manually. If you can’t delete it there either, the issue is definitely a permission setting—not an API problem.

内容的提问来源于stack exchange，提问作者RJBreneman