Our main internet connection is Windstream and we have a backup Verizon DSL line. The Windstream connection uses a Linksys RV220W router. We manually switch the cable to the DSL Westell router if ever needed.
We were starting to experience random network issues. Some computers were getting random errors in our Database software and ping tests showed some small packet loss. When we switch over to DSL, the problems immediately go away. If we switch back to the Windstream connection, the issues come back, but not right away. Normally it takes an hour or so but ALWAYS comes back. We replaced the RV220W router and upgraded the firmware in it. Our 2 servers are fully patched. I've done a deep malware scan on both servers. The only thing that makes sense to me is some kind of flood attach to the Windstream IP address. Unfortunately the RV220W logs don't tell me much. Any ideas?
Here's a test you could do to at least doublecheck yourself and isolate the issue.
Switch over to DSL for the time being, since that's a stable connection.
Connect a computer or small test network directly to the Windstream pipe, and see if the creeping errors recur, or if it stays clean. You'll likely have to re-address whatever computer you connect to the Windstream pipe unless they hand out DHCP to you, but it'd be a good way to show Windstream 'this connection suffers packet loss/latency/other issues separate of any of our internal infrastructure'.