Thanks for your support, I am trying to do this but to be honest I don't know
how to arm the failure route for this case of "fr_inv_timer".

When I received reply 183 I use t_set_fr() function to set the new value for "fr_inv_timer",

do far so good, but I never received failure_route[0] when Kamailio terminate the call sending 408,

even calling like this:

t_on_failure("0");
t_relay();

I can't find on documentation how to do this.
Thanks a lot