Scheduled site workflows Run Twice

I am using Nintex workflows for SharePoint 2019. Recently I migrated from SP2013 to SP2019. I scheduled site workflow to run once a day. The job of workflow is to send email notification report every day. 

I am receiving the notification twice. To avoid double notification I tried the following actions. 

1. I deleted the schedule. Now, there is no schedule to run the workflow.
2. Verified Nintex database, [WorkflowSchedule] table, there is no record related to the workflow.
3. Workflow instance is also not started because i deleted schedule.
4.  verified central administration, i can see only one instance of “Nintex Workflow scheduler” job.

Now i am receiving one notification. the question is from where this notification is triggered? 

Kindly suggest the points to find this.