Loud microphone feedback when answering by app

I just installed the Ring Intercom to the Bticino 344702 station. Wiring instructions were easy however confusing, since it said to install wire 1 to BUS and wire 2 to BUS, also. There happened to be 2 slots in the station called BUS so I took a guess as to which wire to attach to which BUS slot. It seems I guessed correctly (50/50 chance after all) since the station was detected by the Ring Intercom, and I was able to open the door remotely with the app. But the problem arose when I tested answering the door by app when someone presses the doorbell. The app is notified and I can pick up, but as soon as I do, the speaker outside lets out a super loud, high-pitched squeal, very much like microphone feedback. Muting the mic on the app does nothing, nor does playing with the speaker and microphone levels in the Device settings. I even tried to wire it the other way (switch around wires 1 and 2 to be in each other's slots, since it wasn't clear which one was which anyway) but that disabled the device entirely, so I switched again back to the original configuration. So now I have a set up that works great as remote unlock (which was the main reason I bought it) but is pretty much useless as an actual intercom. Does anyone else have a similar issue, or know a solution? TIA.