Workflow notifications are being sent out multiple time for same expense report

We have a couple of users that are getting 2 workflow notifications of their expense reimbursements.  These notification are being sent 2 seconds apart from each other.  See example below.  Would anyone know why this is happening and how we can stop multiple emails being sent to the user? 

Also we have another issue where if the attachment size is too big to send the approval notifications to the manager, the system the sends the Undeliverable workflow notification to our Process folder every 2 minutes.  This causes our table space to be get full.  How can we resolve this issue and what can be causing this?