We’ve had problems with 2019-12 Security Monthly Quality Rollup for Windows Server 2012 released on 10 Dec 2019 (KB4530691) bringing down 3 of our customers servers in a Rackspace environment. If you are running Windows Server 2012 I would recommend changing your update settings to this:
to stop it being automatically applied, and testing the update in a non-production environment before applying it to a production server. It put our servers into a continuous boot loop, forcing restoration of the servers from backup images.