Not working properly with S10+ since Android 10 update

I've had a Floodlight Cam for just over a year and everything has been working perfectly, other than the occasional need to clear data to get rid of lag. However, now my Floodlight Cam works perfectly on my Echo Show, but on my Samsung S10+ I can't hear the person at the door, although they can hear me fine. Both the Show and the S10+ are on the same network (other than when the phone is on 4G obviously). On playback of recordings the audio is perfectly legible on both ends. I installed the Ring app on an old Samsung S7 Edge, and voila, it worked perfectly, audio hearable at both ends of the connection on live stream. Switch back to the S10+ and problem comes back. S10+ had an update to Android 10, before which there were no issues with the audio on the S10+, which leads me to believe there is an issue somewhere between the app and Android 10. I've been in contact with Ring support, who asked me some questions which were completely irrelevant, and who told me they escalated it to a specialist team. Haven't heard anything back for 19 days (and counting) and my emails are now being ignored. Things that are NOT the problem: Internet connection: I have 350mbps down, 40mbps up, and in actual fact average speed is around 376mbps down and 42mbps up Wireless connection: I have a Netgear R8500 and a Netgear EX7500 mesh extender. The EX7500 is designed to mesh with the R8500 using the same SSID. The R8500 is about 30 feet from the floodlight cam, and the EX7500 is about 10 feet from the cam. There is one wall between the cam and the EX7500. The RSSI signal on the S10+ varies between around 43 and 53. WiFi channel: My router and extender automatically switch to least crowded channel. In any case, I have checked with several WiFi analyzer programmes, on both Android and Windows and there is no appreciable congestion. My Echo Show connects to the EX7500 and when I stand in exactly the same place as my Echo Show with the Samsung S10+ the problem remains. I'm really hoping this can be fixed, because right now, unless I want to carry around the Echo Show, or downgrade my phone, the Floodlight Cam is useless for one of it's main functions for me - which is to be able to answer the door to delivery people etc when I'm at work.