Help: Mac SmartLink dies after 100 seconds

Works fine on LAN with an Airport Extreme. Also works fine on SmartLink with neighbor’s Wifi router. But at a different location using SmartLink and a different Apple Extreme it dies every time after about 100 seconds. Audio stops. Display stops. Controls still work. I can disconnect.

Windows 7 SmartSDR works fine at this location, same router etc. But SmartSDR for Mac and the Airport seem to have an argument after just a minute and forty seconds of bliss and then refuse to speak to each other. It happens every time. It fails in the same way when using wired Ethernet or Wifi. Airport Extreme says it’s version 7.9.1

Any suggestions?

Thanks

Jon

app SmartSDR for Mac-macOS--1 V1.4.10, D3.9.16 fw:3.1.12 running on x86_64 on macOS Version 10.15.6 (Build 19G2021)