Fritz uses a "pre-loaded route set" to address the proxy. When using a
domain in the Route header
Route: <sip:sip.advancemedia.it;lr>
openser fails to detect that this request is targeted to itself.
(loose_route() compares the URI with "myself" from core) Thus, you have
to add the domain as alias:
alias=sip.advancemedia.it
this should solve your problem
regards
klaus