Ring Intercom: continuous buzzing

Hi there!I just installed my Ring Intercom. It's a great piece of equipment and instructions were clear.However, I do hear a continuous and annoying buzzing on both the Ring app and the building intercom, once I answer the call.But... If I pickup the handset itself, the buzzing goes away and I can talk over the Ring app nicely. So I guess there's some kind of sound feedback/bad wiring going on.Any ideas about where to start?Thanks!