A nmap scan from the Internet (WAN) against a Cisco RV120W shows an open port 916/udp. This port remains open even if one writes an explicit access rule for the firewall.
A quick googling shows that this port is probably used to access the firmware of the router from the outside as well as it has been involved in security problems some years ago. See http://osvdb.org/show/osvdb/34520
If nmap still shows the port opened, I then suggest you to disable the remote management to determine if this is the root of the problem, then contact the Small Business Support Center to have a TAC engineer figure this out;
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