CAME BPT E/272 feedback sound when answered by app

I have a CAME BPT E/272 which I am trying to connect to a Ring Intercom.Whenever I buzz the intercom and answer with the E/272, it works fine.If I try to answer with the app, I keep hearing a loud feedback sound, as if the mic and speaker are feeding into each other. I can talk over it and be heard by the person buzzing as well as hear the other person talk back but it's extremely uncomfortable with this feedback sound present.Soon as I hang up, the sound goes away. Muting the app mic or adjusting the app volume for mic and speaker as well as the hardware mic potentiometer on the E/272, makes no difference in reducing this feedback sound.I have wired:Intercom A cable A2 to 6 on the E/272A5 to 8A3 to 4A1 to 5A6 to 7A4 is not connected to anything.The above worked well for the E/272 predecessor with the same wiring, the BPT SA/72Any help, appreciated!