Event duplication is usually caused by another calendar syncing process running at the same time as Cirrus Insight Calendar Sync. We'd recommend connecting with your Salesforce admin to see if your org is currently using (or has used in the past) any other calendar syncing applications such as Salesforce for Outlook, Ebsta, Yesware, or Appirio Cloud Sync.
Those processes need to be completely disabled, uninstalled, and blocked in Salesforce to avoid event duplication. One area that's often overlooked is Connected Apps Oauth Usage under the Manage Apps section in Setup. Salesforce provides some helpful information about revoking/blocking apps here:
"Salesforce - Monitor Usage for Connected Apps"
If you don't find any other calendar syncing applications within Connected Apps Oauth Usage, please contact Support and provide the following:
In order to maintain performance and stability while also reducing customer resource drain, the default sync interval will be increased from 5 minutes to 2 hours as of 4/21/2021.
For Admins: How can I use Google Organizational Units to set up Admin-Managed Sync?
To only provide certain users with access to Cirrus Insight Cloud App, your G Suite admin can designate which Organizational Units (OUs) should have access.
Why was I notified about a problem with my Calendar or Email Sync?
Cirrus Insight will send daily emails with specific steps to fix the Calendar or Email Syncissue until you take action to resolve it.
How do I authorize my Office 365 account when Calendar Sync encounters a problem?
If you received an email with the subject "Cirrus Insight Calendar Sync Problem," that means Calendar Sync wasn't able to access your calendar and you'll need to grant authorization.
For Admins: How can I set up Calendar Sync with multiple Exchange service accounts?
Learn how to set up Cirrus Insight Calendar Sync with multiple Exchange service accounts.