Strange DPMA issues / periodically can't connect to config server


I have been having a persistent issue lately. We have a local LAN with multiple D62 phones configured to asterisk via DPMA. No issues on the local end. Phones are auto-configured through their MAC address /mDNS.

We have one remote user who connects through an IPSec VPN (Fortigate to fortigate). It seems that roughly once a week he loses connectivity on his phone, and it shows him as offline. Calls to him go straight to voicemail. We configure the configuration server address manually on his phone.

We have him go to settings, and “reconfigure” and no matter what, it cannot communicate with the digium configuration server. We even do a factory reset, pop in the digium configuration server IP/port again, and it times out trying to connect to the server.

His local LAN has complete access, through the VPN, to our internal VOIP network. I can connect remotely to his phone’s web interface, can ping the phone, his network can ping our configuration server. port 5060 is open for him as well on the linux firewall, no network issues whatsoever that I can find.

I do a module reload on the asterisk server for the DPMA module. Still, he cannot connect to the configuration server.

Only when I do an asterisk “core reload”, or restart the asterisk process, he is immediately able to communicate/configure with the configuration server.

I have DPMA logs enabled but it’s showing me only very basic info, and no errors of any kind…

Anyone have any ideas on what might be going on here?

Asterisk 11.23.1
DPMA version 11.0_3.3.2

Thank you very much…