What does HTTP 302 mean exactly?
The HTTP response status code 302 Found is a common way of performing URL redirection.
The 302 Found is not an error but a redirect to a temporary location. You could resend the request to the new location received in the response header.
The 302 status code indicates that the resource you are requesting has redirected to another resource.
If this is behind some authentication, or requiring a session to be active then yes, it would follow that the session timing out is responsible for the Ajax resource being called to redirect to possibly a login screen maybe.