This has gotten to be fairly serious. When some users start an problem ticket, when a service desk agent assigns a ticket, or sometimes for any arbitrary change at all, JSM will return a
Communications Breakdown
The Jira server was contacted but has returned an error response. We are unsure of the result of this operation.
Close this dialog and press refresh in your browser"
I am running JSM 5.3.0, but the problem has persisted since 4.x. I also run Confluence on the same system at a different port.