Calendar callback hangs if formsauth login has timed out

Hi, I'm hoping someone has experienced this and has a solution or work-around. We are using the daypilot calendar on a page and most of the handling is done via jQuery, JSON, and callbacks. The problem we experience is the issue of if the user's session or login times out, the next action within the calendar will cause the page to hang with the promise of the calendar updating, but it never does. The page cycle in the background has tried or is trying to redirect the user back to the login page, but because the request is from a callback, the redirect doesn't occur. Is there an event or control I can include for the calendar so that it checks timeouts or can handle an expiry redirect if needed? Any help is appreciated. If possible, I don't want to use a 'keep-alive' timer, as I don't want the page to be kept alive, I do want the login to timeout and redirect the user back to login again. Thanks.