Simple scenario:
sipp 127.0.0.1:5070 -sn 3pcc-C-A -3pcc 127.0.0.1:9000 -i 127.0.0.1 -p 5060 -m 1 -trace_msg
sipp 127.0.0.1:5071 -sn 3pcc-C-B -3pcc 127.0.0.1:9000 -i 127.0.0.1 -p 5061 -m 1

Caller sending this INVITE:
INVITE sip:service@127.0.0.1:5070 SIP/2.0
Via: SIP/2.0/UDP 127.0.0.1:49239;branch=z9hG4bK-22997-1-0
From: sipp sip:sipp@127.0.0.1:49239;tag=22997SIPpTag031
To: service sip:service@127.0.0.1:5070
Call-ID: 1-22997@127.0.0.1
CSeq: 1 INVITE
Contact: sip:sipp@127.0.0.1:49239
Max-Forwards: 70
Subject: Performance Test
Content-Length: 0

The local port should be 5060 not 49239.
This working correctly in version 3.4.1