We are also experiencing the issue on multiple email sending in our approval workflow. We already sent to Smartsheet Support for checking and resolution 3 days ago but still waiting for the response.
This happens only when the approver declines the request and per workflow should provide for the reason for declining the request. The email requesting the approver to indicate the reason in the comment box is being sent 8-10 times.
Please share how you resolved this issue.
Thanks and regards