On a production windows server we sometimes receive empty value for "host_metadata".
We use:

HostnameItem=system.run[cmd /Q /S /C "for /f "usebackq tokens=1" %d in (`wmic computersystem get domain ^| find "edu"`) do (for /f %h in ('hostname') do @echo %h.%d)"]

HostMetadataItem=system.uname

This issue seems started from agent upgrade 4.0 -> 5.0.3
It happens only on some win servers. We could not go back and downgrade agents to 4.0 on affected servers.

We tested "system.uname" key as a passive check but it always worked and returned a value.

We store agent log to eventlog and when issue happens we saw this warning:

cannot get host metadata using "system.uname" item specified by "HostMetadataItem" configuration parameter