RT 4.4.2 & CAS authentication & "History..."


I have a RT 4.4.2 server with CAS external authentication, running well, however occasionally when a user selects a ticket the History section fails to load. displaying “History…”

in the browser i receive a:
Access to XMLHttpRequest at '" (redirected from ‘/Helpers/TicketHistory?id=XXXXX’) from origin ‘’ has been blocked by CORS policy: Response to preflight request doesn’t pass access control check: No ‘Access-Control-Allow-Origin’ header is present on the requested resource.

if a user refreshes the RT home page and returns to the ticket page the history will load normally.

Since it works some of the time i’m currently pursuing this as a CAS ticket expiration issue but i’m not sure where to investigate further.

Anybody have a quick fix?