Intermittant Audio problems

My system is Freepbx 2.11 distro. This is bsically a new install. We replaced an IPitomy IP1100 due to licensing issues with them. The phones are the IPitoy HD series phones. All the phones were defaulted and hand programmed. We have a Grandstream GXW4104 for the pots lines. Other than the ports for programming the system 8088 and 22 there are no outside ports forwarded to the system. Since day one (10 Days ago) we have had intermittant calls being dropped. I have TCPDump running collecting UDP traffic on the system. I have yet to see a call get dropped. I do see an entry like this: Zenginko-1 on port 5020 from the grandstream trying to connect to udp port 10006 at the system. I googled this Zengink0-1 and wasn’t able to find anything definitive. It ALWAYS tries to connect to port 10006. Anyone know what this might be?