Xfinity stream audio video not synced

To start, This has been going on for months.  I've deleted and reinstalled the app, the TV Wi-Fi is very fast and stable, there is no traffic on the WiFi that should be creating any issues and there is no sync issue on ESPN app, Netflix or other streaming apps ... Just Xfinity stream.  Why does the audio/video become out of sync on any channel viewed?  Extremely frustrating.