Apple released the latest macOS Monterey 12.3 update to the public earlier this week. While the new build packs a plethora of new features and performance enhancements, it seems to be bricking some Macs that had a replaced logic board. According to numerous reports, users are not able to get their Mac in a working state. Scroll down to read more details on the subject.
Apple's Latest macOS Monterey 12.3 Update is Bricking Macs for Users Who Had Their Logic Boards Replaced
Users have shared their grief on Apple's Developer forum thread, citing that updating to the latest macOS 12.3 build leads their Macs to endless restart loops, errors, and ultimately bricking them. Take note that the new update only affects Macs that had their logic boards replaced, specifically Apple's new 14-inch and 16-inch MacBook Pro models.
There is a firmware bug in Mac OS 12.3 that renders the update impossible to install on any 2021 14 or 16 inch MacBook Pro that has had it's logic board replaced.
The cycle is:
You try to upgrade, the upgrade will fail but recovery to handle it correctly, you'll reboot still on 12.2.1 but with a report a problem dialogue informing you of an iBoot Panic
You'll try to upgrade again. This time, the iBoot FW will corrupt. You'll see the apple icon flash on boot 5-6 times before seeing the exclamation mark symbol telling you recovery is needed.
You can try and revive using a second Mac with Apple Configurator 2. This will fail, because it tries to load the 12.3 firmware from the IPSW, in either DFU or Recovery mode.
The only way to get things running again is to manually download the 12.2.1 IPSW and use Apple Configurator 2, with the Mac in DFU mode, to load the revive image. This will update the firmware of iBoot, and the recovery image to a working build. The Mac will then restore 12.2.1's OS, keeping your data upon finishing.
As per the reports of macOS 12.3 bricking Macs, there are two potential results faced by users. In one situation, the Mac is bricked that can not be further used. In another situation, the Mac finishes the macOS 12.3 update process and reboots to nothing but an "iBoot Panic" message. The reports are also filed on Reddit where a user states:
"When I attempt to upgrade to 12.3 on a 2021 M1 14 inch macbook, the entire download and then upgrade sequence completes (30 or 40 minutes in upgrade sequence) and when it reboots has not upgraded and is still on 12.2.1,"
If the Mac does not wake up after the update, users have to manually put their machine in DFU mode and revive it. However, it requires the use of a secondary Mac. While the problems persist, one user has advised the following:
Any attempts to get 12.3 on your mac will fail with that error.
You should be able to get into DFU though - wait until you're on the exclamation mark screen after a few flashes, then do the DFU key sequence. Configurator will let you try a revive in recovery mode though, but not sure if that works - I assume that's your 21 error. You should get a 2006 error when trying in DFU mode.
The second time I tried a normal in system upgrade, the screen refused to show anything as a result of the firmware failure - but it still appeared in Configurator and the DFU key sequence still worked.
We will share more details on the subject as soon as further details are available. Are you experiencing macOS 12.3 bricking your Macs? Let us know your thoughts in the comments section below.