The system automation tasks are generating two invoices for each client: one invoice contains the expect line item, and the second item is empty.

Clients receive two copies of payment overdue reminder emails.

The server is running the cron.php script twice at the same time, triggering the daily automation tasks to run twice simultaneously.

To check whether this is the cause of the issue:

1. Log in to the WHMCS Admin Area.
2. Go to Configuration > System Logs.
3. Use the Search Filter tab to search forCron Job: Starting Daily Automation Tasks.
4. Observe the Date column next to the entries.

Two or more entries with the same timestamp confirm that this is the issue:

To resolve this issue:

1. Review the crontab on your server. You should see one entry running the cron.php file once every 5 minutes.
2. Find any duplicate entries and remove them.

In the example below, you would remove the second entry (2):