[Serusers] loose_route bug?!

Hi Everyone, I am using SER version Server: Sip EXpress router (0.9.2 (i386/linux)). I am initiating a call from a caller sip UA to a callee sip UA and I am receiving the ACK response to the INVITE from the callee on SER. Before loose_route processing it looks like this: ACK sip:2224440133@10.1.10.65:5060 SIP/2.0 Via: SIP/2.0/UDP 172.16.15.52:5060;rport;branch=z9hG4bK83e54f590401584628d473053d1ef8a8 From: <sip:2224440132@xxx.yyy.zzz:5060>;tag=1cac2190 To: <sip:2224440131@xxx.yyy.zzz:5060>;tag=d323038ba423a329i0 Call-ID: 66cb6ba85191e6025ebde2c552177442(a)172.16.15.52 CSeq: 1 ACK Contact: <sip:2224440132@172.16.15.52:5060> Max-Forwards: 70 Route: <sip:10.1.10.65;ftag=1cac2190;lr>,<sip:10.1.10.65;ftag=1cac2190;lr> Content-Length: 0 After loose_route processing and relaying, the ACK, instead of being routed to the callee (2224440133) User Agent, it is received back at SER looking like this: ACK sip:10.1.10.65;ftag=1cac2190;lr SIP/2.0 Record-Route: <sip:10.1.10.65;ftag=1cac2190;lr=on> Via: SIP/2.0/UDP 10.1.10.65;branch=0 Via: SIP/2.0/UDP 172.16.15.52:5060;rport=5060;branch=z9hG4bK83e54f590401584628d473053d1ef 8a8 From: <sip:2224440132@xxx.yyy.zzz:5060>;tag=1cac2190 To: <sip:2224440131@xxx.yyy.zzz:5060>;tag=d323038ba423a329i0 Call-ID: 66cb6ba85191e6025ebde2c552177442(a)172.16.15.52 CSeq: 1 ACK Contact: <sip:2224440132@172.16.15.52:5060> Max-Forwards: 16 Route: Content-Length: 0 Why is SER routing this ACK request incorrectly?! Is the syntax of the original ACK generated by the Callee's UA incorrect?! I would appreciate any help as I can't figure it whether there is something wrong with ACK's syntax or there is a bug in SER's loose_route processing?! Thanks a lot ramin