[Users] cancel method problem

[unplug]

When UA1 makes a call to UA2, both ringing.  Then UA1 cancels the
call, a strange log message (from ngrep) will be got below.  After
that UA2 will ring 3 times itself.  You can see in line 718, there is
a cancel method.  After that, there are many Record-Route, Via in the
sip CANCEL method (line 763, line 1578 and many).  Does anyone know
what the problem is?

http://meerkat.no-ip.com/openser/cancel.log