Scheduled Emails Delay and duplications

We are using Hangfire 1.6.17 in Asp.net Core and SQL Server Azure to schedule emails to be sent to subscribers.
A RecurringJob is created to check for scheduled messages to be sent by email.
We are facing an issue that sometimes the message is sent multiple times with a delay. let's say the message is scheduled to be sent at 6:30. Its sent at 6:32 with duplication.
Any suggestion to fix this issue?
Thank you

Start with the RecurringJob setup and Hangfire server logs around the 6:30–6:32 window; compare the scheduled job history with email-send records. A useful resolution would identify whether the delay and duplication come from scheduling, retries, or the email handler, then document a reproducible fix for Hangfire 1.6.17 on ASP.NET Core with Azure SQL Server.

Written by the indexing model from the issue text.