Short post this time. After all the mess that happened after the Spectre and Meltdown vulnerabilities disclosure and a frenzy of patching (i think Microsoft has released updates 5-6 times in January) a few machines in our network have stopped updating their status in WSUS. Although, they were still able to check for updates. It happened after a failed installation of KB4056892 update. Which then installed correctly, but since then no status updates were sent. The solution is as per usual: stop the Windows Update service, wipe C:\Windows\SoftwareDistribution folder, start the service and run the check for updates.