Typically when you see “Object reference not set to an instance of an object” errors from the fog client, this most typically means tge encryption needs reset for that host.
the reset can be done from the web gui, on the host’s general page. It’s a big button towards the top.
If this fails to fix the issue, try reinstalling the client on that box. Make sure there are reboots between Uninstall and reinstall.
If several hosts have the issue, this points to an image problem - perhaps reboots were not done (two at least) prior to capture after all software has been installed.