[Freeswitch-users] The Sipml5 cannot register to freeswitch

I found that sometimes the sipml5 client can not register to freeswitch.When I use tcpdump to capture the packet I can see the three-way handshake,but I execute show channels on the freeswitch can not see my channel.Then after several minutes,I re-try call,successful. Why?Could you help me?