This normally indicates a network problem, most commonly a bad router or Wifi Node at the user's location.
With more recent versions (April 2023 and later) both the Admin Console and the MMC Application provide a new WebSocket column which will show if there have been WebSocket errors or so many that the WebSocket is "Broken" and the client javascript has downgraded the connection to Ajax HTTP Web server calls only.
When a user identity option is active (Windows Security, SAML, OpenID and so on), the user's I.D. which is frequently an email address will be displayed--if the WebSocket column shows errors it is a strong indicator that the network equipment at that user's location has problems.
