Ticket Status manually changed to resolved will automatically change back to open


I’m working on a problem regarding user management and ticket modification.

I have normal privileged users and others.
“Everyone” (in a global context) has the following rights:
CreateTicketModifySelfReplyToTicketModifyTicket (tried it with and without this right, actually i dont want to set this right for everyone)“Privileged” can addiationally
OwnTicketNow there is another group of users which should not have as much rights as privileged users but more rights than everyone. These people are external users which have the privilege to work on tickets like supporter (privileged users). Due to the fact that many many external users could get such a specific status, i dont want to add them to a group manually.

As a supporter, I created a ticket, threw it into an “External”-Queue and as the requestor I set the external users email address. The user has been created, he can access RT but is not allowed to have any additional rights. Im fine with that.

When I login as this external user, i want to change the ticket status to resolved (via the self-service-interface) and therefor I click on the ticket —> Reply or Comment —> and change the status of the ticket out of the drop-down-menu.

The History tells me: Ticketstatus changed from opened to resolved (thats what i want) —> But at the same second RT does this automatically: —> Ticketstatus changed from resolved to opened (thats not what i want)

So why does RT change the status back to open automatically? If i wouldnt have the permission to change the status, wouldnt it tell me: “Not allowed” or something?

Does anyone know which additional rights i must set so that predefined external unprivileged users can change the status of their own tickets?

Best regards,