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I see. I don't think having other stuff plugged in is a huge problem though. I had my AirPods plugged in to the monitor and I have a Belkin Ethernet adapter too as well as a headset on a USB-C to 3.5mm adapter. Maybe your first monitor was a lemon but I would hope Apple has tested updates with other peripherals plugged in.No.
The full story is...
The first time I tried the 16.4 update, I had a Belkin ethernet adaptor, stream deck and usb-c mic, as well as the TB connection plugged into the ASD, with the TB connection to my MBPro 14" M1 Pro going via an extension TB cable. I've updated the ASD using this setup in the past with no issues but for 16.4 it bricked.
I took the ASD to my (very) local Apple Store and after about an hour of trying they managed to get it back up and working.
I then tried the 16.4 update again but this time with a direct TB connection between ASD and MBP with nothing else plugged into the ASD (I also put my MBP on external power) - however, the same result, it bricked again. I took it back to the Apple store and they are now replacing the logic board as they feel this is at fault?
I purchased a new ASD to continue working and updated to 16.4 with the direct connection first time, no problem (it took about 6 minutes in total)