[Serusers] Some questions on "loose_route"

Hi all again, from various examples in the SER admin_guide and my own SIP knowledge-base I conclude, that the action "loose-route()" is responsible for correct routing of those requests, that are not destined to the proxy (host of Request-URI is not the proxy) and that have a proper Route-header indicating "loose-routing". As such the action "loose_route()" should be sufficient to modify the Request in such a way, that the following action "t-relay()" finishes processing of the request. Therefore the action short sequence ... if (loose_route()) { t_relay(); break; }; does all, what is necessary for loose routing of those requests. My problem is, that I could not produce a condition, where "loose_route()" evaluates to true, so that the action block { t_relay(); break; } is executed. I expect, that in a simple call-scenario with one record-routing SIP proxy (SER) the routing of the ACK- and the BYE-method should trigger the above mentioned "loose_route()" action. But unfortunately it does not. Why? Please help (in best case confirm) my understanding of "loose_route()". Franz