I usually use the xert workout player for garmin in combination with having the workout on my computer screen at the same time. But the screen on my computer is extremely laggy. There is about 2-5 sec between every update of the watts, HR, etc numbers which makes it almost useless.
What could be the problem? There is maybe 1-1,5 meters between my desktop computer and my garmin, and another 0,5 meter between my powermeter/trainer and my garmin.
Try running the workout with EBC on your phone next time.
If no lag on EBC the issue is with how Garmin is processing the telemetry data from the Connect IQ app via Bluetooth to Garmin Connect on your phone which in turn passes the data on to XO. Try disabling Wi-Fi on the Garmin to see if that make a difference.
If the same lag occurs with EBC there is an issue with XO server connection to your location.
The workout player needs to access Xert’s servers (to send your data via telemetry) via your phone’s internet connection. The telemetry can’t be sent via the Garmin’s Wi-Fi connection, unfortunately.