Hello @wabyrd,
I am glad for you that you could find the config problem. 
For the loss of registration, this can be many things. Usually the only thing I recommend that fixes almost all the issues on SIP earth is to implement TLS connection. If you can do that with your device and are not doing it right now, this is the next move I would recommend. Otherwise, if you already use TLS, well, this will be trickier to find the reason why.
Check the wiki help, this is a bit tricky, but once implemented it should fix all your current connection issues (and avoid all the future ones you will never know about 
). I am a bit exaggerating here, but bottom line, most of such problems are often solved when doing so.
If you feel like having some technical reasons of why, you can check:
Kind regards,
Alexandre