SIP register fail after first register.

I setup FreeSwitch as my VoIP server on my router, and let OBi110 to register onto the VoIP server. I found that it will show register fail in 60S after rebooting. The error shows that "No Response From Server"

Here is the syslog information, it looks that FreeSwitch will response the OBi110 at first. While OBi110 success to register to FreeSwitch, OBi110 will always send out a package as "sendto 725bc70f:5080(286)", and FreeSwitch will stop response after it.

<7> sendto 725bc70f:5080(536)
   192.168.100.239   30/06 00:32:58.312
<7> sendto 725bc70f:5080(536)
   192.168.100.239   30/06 00:32:59.343
<7> RxFrom:725bc70f:5080
   192.168.100.239   30/06 00:32:59.343
<7> SPREG:Subst Contact w/ via-rport 5061
   192.168.100.239   30/06 00:32:59.359
<7> RxFrom:725bc70f:5080
   192.168.100.239   30/06 00:32:59.359
<7> sendto 725bc70f:5080(783)
   192.168.100.239   30/06 00:32:59.359
<7> RxFrom:725bc70f:5080
   192.168.100.239   30/06 00:32:59.375
<7> SPREG:Subst Contact w/ via-rport 5061
   192.168.100.239   30/06 00:32:59.375
<7> REG:OK(30)
   192.168.100.239   30/06 00:32:59.375
<7> RxFrom:725bc70f:5080
   192.168.100.239   30/06 00:32:59.468
<7> sendto 725bc70f:5080(286)
   192.168.100.239   30/06 00:32:59.468
<7> sendto 725bc70f:5080(783)
   192.168.100.239   30/06 00:33:29.390
<7> sendto 725bc70f:5080(783)
   192.168.100.239   30/06 00:33:29.875
<7> sendto 725bc70f:5080(783)
   192.168.100.239   30/06 00:33:30.875
<7> sendto 725bc70f:5080(783)
   192.168.100.239   30/06 00:33:32.890
<7> sendto 725bc70f:5080(783)
   192.168.100.239   30/06 00:33:36.890
<7> sendto 725bc70f:5080(783)
   192.168.100.239   30/06 00:33:40.890
<7> sendto 725bc70f:5080(783)
   192.168.100.239   30/06 00:33:44.890
<7> sendto 725bc70f:5080(783)
   192.168.100.239   30/06 00:33:48.890
<7> sendto 725bc70f:5080(783)
   192.168.100.239   30/06 00:33:52.890
<7> sendto 725bc70f:5080(783)
   192.168.100.239   30/06 00:33:56.890
<7> sendto 725bc70f:5080(783)
   192.168.100.239   30/06 00:34:00.890
<7> REG:Timeout; retry in 3000 ticks
   192.168.100.239   30/06 00:34:01.390
<7> sendto 725bc70f:5080(783)
   192.168.100.239   30/06 00:34:31.390
<7> sendto 725bc70f:5080(783)
   192.168.100.239   30/06 00:34:31.890
<7> sendto 725bc70f:5080(783)
   192.168.100.239   30/06 00:34:32.890
<7> sendto 725bc70f:5080(783)
   192.168.100.239   30/06 00:34:34.890
<7> sendto 725bc70f:5080(783)
   192.168.100.239   30/06 00:34:38.890
<7> sendto 725bc70f:5080(783)
   192.168.100.239   30/06 00:34:42.906
<7> sendto 725bc70f:5080(783)
   192.168.100.239   30/06 00:34:46.890
<7> sendto 725bc70f:5080(783)
   192.168.100.239   30/06 00:34:50.890
<7> sendto 725bc70f:5080(783)
   192.168.100.239   30/06 00:34:54.906
<7> [PR] prompt transcoding done!!
   192.168.100.239   30/06 00:34:56.156
<7> sendto 725bc70f:5080(783)
   192.168.100.239   30/06 00:34:58.906
<7> sendto 725bc70f:5080(783)
   192.168.100.239   30/06 00:35:02.906
<7> REG:Timeout; retry in 3000 ticks
   192.168.100.239   30/06 00:35:03.406