This can happen when you clone Windows endpoints from a template when the template does not account for this problem.
WSUS uses the SusClientId to identify unique devices and then associate the computer’s hostname to the unique identifier for display purposes. The problem is that if SusClientId on several machines are the same and that is what is used by WSUS, then when they report into WSUS conflicts will arise, causing unexpected errors.
If you suspect that multiple machines have the same SusClientId, you can run the following batch command on those machines and compare the output
reg query HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\WindowsUpdate /v SusClientId
How to fix. Run the following from a command prompt as an admin
#Stop the Automatic Updates service
sc stop wuauserv
# Delete the SUSclientID registry key from the following location:
reg delete "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate" /v SUSClientID /f
#Start the Automatic Updates service
sc start wuauserv
#Re-register windows client in WUSS
wuauclt /resetauthorization /detectnow