If computer gets stuck in boot loop from update on deep freeze, 

Right click in deep freeze "end workstation task" 

Then go to zen, find the computer within it's folder. 

Select using box on left, click quick tasks on top bar > refresh device > Quick task status > START

If the computer is able to restart in ZEN, it should be all set, if not, it might require a few reboots or to be disconnected completely from power then rebooted before being refreshed in ZEN