Hi
You might have duplicate SusClientID in your computer park.
If it’s the case only the last computer that reported to the WSUS server will be shown.
As you see always two, I think you have two SusClientID identital for all your park.
To fix please see the script there; https://www.ajtek.ca/wsus/client-machines-not-reporting-to-wsus-properly/ to be run on all your server to reset the client ID.
It can happen if you have cloned from a golden image in exemple.
The link is a good explanation from a Canadian MVP
Thanks
Philippe