I received one of 2018 machines a couple of weeks ago. It worked for a few hours until I tried to install the system update that fixes the CPU throttling issue,

I received one of 2018 machines a couple of weeks ago. It worked for a few hours until I tried to install the system update that fixes the CPU throttling issue, which I assume included a firmware update for the T2 chip. The update failed, and the machine was bricked. Apple have removed everything that isn't controlled by T2 chip. There is no power light on the machine or the charging cable. CPU temperature is the only indicator of power on/off status, as I discovered after removing a very hot machine that I thought was off from my backpack after arriving home. Despite being non-functional, it was actually powered on but spinning the CPU and/or T2 doing god knows what. My replacement unit arrives tomorrow. Wish me luck.