In KitCAT log, incoming messages are logged as follows:
[SipStack-UDPMessageChannelThread-0] INFO gov.nist.javax.sip.stack.SIPTransactionStack - <message
from="135.207.13.73:5060"
..
isSender="false"
The from line sometimes shows incorrect IP address and port number of the sender.
I can provide log file and corresponding packet capture file to show the problem.