If you drop me a short mail at dj0qn (at) darc.de I can send you my networking checklist that should
help you out.
If within the same network, using the radio's internal IP number as the SIP contact will connect them
together. In your case, I assume that you made a mistake, since both have 192.168.0.127.
Also, note that using a 3G/4G router on the radio side will not work unless you get a true IPv4 external
IP address from your provider. By default, you are given an internal IP number that can't be routed. the
Nordic providers seem to be best if giving you a true IP number when you ask, so you may be in luck.
Anyway, I can send you my checklist if you want.
73,
Mitch DJ0QN / K7DX