This type of problem is usually caused by router or even ISP issues. It could be a number of things,
so process of elimination will be the only way to solve it.
To start, make sure that SIP ALG is disabled on both sides. Then turn off the router's firewall to see
if that solves the problem. You may try changing the three UDP ports to see if that makes a
difference, but that rarely helps (unless you have an old RRC running port 5060, which must be
changed).
If that doesn't help, take the control RRC to another location. If it works there, you know that the
problem is on the radio side. Otherwise you can focus on the control side.
I can send you my networking checklist, but it appears that you got things working and probably
don't need it.
73,
Mitch DJ0QN / K7DX