Duplicate tickets are being created by an Email Queue configured to retrieve emails using POP3. The Email Queue is able to retrieve emails but is not able to delete the emails after they are retrieved. This causes the Email Queue to create duplicate tickets each time it retrieves emails from the POP3 email account.
If your Email Queue is able to download emails but is not able to delete emails via POP3, this indicates that there may be service degradation or an ongoing outage with your Email Provider for the Email Queue.
Please check with your Email Provider to confirm if there is a service degradation or outage that is preventing emails from being deleted with POP3. The following is an example of a notice from Exchange Online where their service was unable to delete emails using POP3.