Thanks for your response.
No, I haven't contacted the app developer because it is a weird issue. The SiriusXM app doesn't support Chromecast Audio natively so I cast the audio using Google Home once I launch the app. This worked fine until the current app update. Once I updated the SiriusXM app on my Moto G (2nd Gen) running Android 6.0, the Chromecast Audio (CCA) connection began to drop after 60 minutes. It is almost like clock work. This problem exist on the CCA device at my house and the one at my sister's house. I did a factory reset of the device and was able to download the non updated version of the app. The connection didn't drop for an entire day, until I updated the app to version 4.0. I uninstalled the app and thankfully the "old" version is still on Google Play, not the updated version. I reinstalled it and all is well again. I want to prevent from updating the app because the old version might not be available in the future.
BTW, I have the updated SiriusXM app on two Nougat devices and they don't drop the CCA connection.