From https://www.packer.io/guides/automatic-operating-system-installs/autounattend_windows (emphasis mine):
Finally, your Packer build will be much smoother if the Answer File handles or disables windows updates rather than you tyring to run them using a Packer provisioner. This is because the winrm communicator does not handle the disconnects caused by automatic reboots in Windows updates well, and the disconnections can fail a build.
I have googled but I can’t seem to find any reference for how to do this. Any one able to provide some help?
If someone can help me I’ll submit a pull request for the docs explaining how to do this.