Most likely this is a timing issue. Do you have any hardware installed to use as a timing device? If not, make sure that your are using a reliable timing source. This will cause so much headache and randomness if you do not configure it properly. I had a conference room set up and working but had a lot of delay due to the same issue. It didn’t garble the call, it simply delayed the playback between speakers by 2 seconds. This was annoying until I fixed the timing issue.