[SR-Users] issue with tm callbacks / premature cancel

I've got stuck today trying to implement some sequential forking scenario. When the call comes destined to the local user, I'm trying to reach it sequentially through two alternative extensions. For each extension, I'm calling t_set_fr with a timeout of 15sec. They reply only 180 and do not pick up the phone. After that the call should go to the "last resort" PSTN number. I'm calling then t_set_fr with a timeout of 30sec. But immediately after sending INVITE to PSTN gw Kamailio generates cancel and sends 408 Request Timeout to the initial INVITE. In the debug log I'm seeing this: Aug 1 17:34:43 localhost /usr/local/sbin/kamailio[28488]: DEBUG: tm [t_hooks.c:288]: DBG: trans=0xb60f543c, callback type 1048576, id 0 entered Aug 1 17:34:43 localhost /usr/local/sbin/kamailio[28488]: DEBUG: tm [t_reply.c:1634]: DEBUG: relay_reply: branch=1, save=1, relay=-1 Aug 1 17:34:43 localhost /usr/local/sbin/kamailio[28488]: DEBUG: tm [t_cancel.c:328]: DEBUG: cancel_branch: sending cancel... Does it look like something familiar to you? Kamailio version: 3.1.4 Config of tm module: modparam("tm", "fr_timer", 20000) modparam("tm", "fr_inv_timer", 120000) modparam("tm", "restart_fr_on_each_reply", 1) The rest of config is really simple, I can upload it somewhere if it's necessary. -- Sincerely, Andrew Pogrebennyk