Symptoms

Client reported that staff that uses SmartActions for WorklistItem approval are getting duplicate responses.
First response will be that the WorklistItem has been actioned, and the second one will be an error stating the following:
The K2 server could not find the worklist item 895499_72. This item may have been actioned by another user.
The full error from the K2 server is 'The worklist item 895499_72 is no longer available or you do not have rights to open it.'.
 

Diagnoses

We looked at the properties of each of the mails coming through and found the IP Addresses (Property: X-Originating-IP: :IP_ADDRESS])
 

Resolution

These were different K2 Servers that used the same SmartActions account for SmartActions and thus also replying to the emails.
Once we changed the servers to use different accounts the issue was resolved.