If the PPMs change value once every minute, the most likely cause is anti-virus scanners holding all the data until the transaction "completes" before passing it to the GUI. The PPM information is ongoing data, so does not have a completion point.
Tieline suggests adding an exception for the codecs. This thread explains how to resolve the issue with Sophos:
"One workaround (which wouldn't require you to turn off the feature) would be to add a website authorization for the source IP of the stream. So for Sophos Home it would be under the devices configuration - 'Web Protection Exceptions'. For SEC managed it would be under the AV policy as a website authorization and for Cloud you could put it under: https://cloud.sophos.com/manage/config/settings/scanning-exclusions as a website exclusion."
Other anti-virus programs should have a similar option to add an exception for the codec IP address.