Joining the club as well. 2016 MacBook Pro with Touch Bar. All working OK then one evening left off charge and battery went flat, plugged back in and booted up only to be greeted with the Critical update error. As others Safe Mode boot is fine. Tried all the tricks mentioned about waiting a few minutes before pressing "Try Again" button, using different networks, wifi and ethernet cable but the update always fails. Tried upgrade of OS to Big Sur still have the same message. Tried clean install of Big Sur and still have the same message. Took machine to local Apple authorised service provider who repeated all of the above, after a while a second set of diagnostics stated it needed a new upper case as the Touch Bar did fail a diagnostic test. Cost circ £600. Trying one more repairer who states they have had a 50% success rate with this when they get the soldering iron out on the machines but still around £400 to do the work. Really wish Apple would recognise there is a common problem.