We noticed starting a few months ago that some calls that come in through our ring central number sometimes drop or no audio comes through and they hang up. We didn't notice it in the beginning, thinking they were those drop robocalls, but sometimes they were potential clients.

We use the local network Cox, with a Netgear router. The 2 landline phones we use are connected to the router through ethernet cables, and 1 mobile phone that uses the app.

We don't think know if it is the network, because when a call comes through and is answered through mobile, the call still drops and he has to call them back. It didn't do that before, which is why we caught on now, because now even incoming calls on the mobile get dropped.

No changes have been made in the time we have used Ring Central. I've tried diagnosing the issue using the resources already on Ring Central, but troubleshooting and checking the ISP has not shown any problems on our end.

This is only through incoming calls, we have no issue making outgoing calls.

What are some possible causes and how would I diagnose this issue?