The #1 cause of audio echo/looping is when someone is watching their stream from the system they're streaming from.
The #2 cause of audio echo is if someone has set their desktop/mic device multiple times in Settings->Audio; only one of each Desktop and Mic should be set, all the others should be Disabled.
The #3 cause of echo is that someone set up their webcam and did not disable the mic on it.
Do a brief 30-second test recording, then go into the Help menu, Log Files, Upload Current Logfile and paste the URL it gives you here. We can take a look and see what's going on.