T2 chip still causes unexpected restarts for no known reason

A reader has drawn our attention to a bug that affects Mac users with the Apple T2 chip running macOS Catalina. On the forums of Apple, dozens of testimonies evoke this problem, with different contexts, but always the same result. When the bug occurs, the Mac unexpectedly restarts, often blowing its fans at their maximum speed for a short period of time, and displays this message at startup:

BAD MAGIC! (flag set in iBoot panic header), no macOS panic log available
On restart, here is the only information displayed by macOS.

What is this bad magic? It is difficult to know, since as the message indicates, there is no log associated with the crash of macOS. Normally, the logs record everything that happens on the Mac and they are a precious ally for understanding the origin of a bug or a crash. Otherwise, we are limited to assumptions based on testimony.

All the cases referenced on the Apple forums have two things in common: the crash only concerns Macs with a T2 chip and where macOS Catalina is installed. The first seems undeniable, it has never been listed on a Mac without this ARM chip responsible for the security of recent Apple computers. All models are affected, however, from MacBook Pro to Mac mini in 2018, including the iMac Pro and even the all-new Mac Pro.

The association between the bug and macOS Catalina is misleading, however. The latest version of Apple’s system appears to have exacerbated the problem, and the error message has changed. But these unexpected restarts are not new, they were already mentioned in 2018 about the iMac Pro under High Sierra. At the time, we never knew what was causing this bug, and unfortunately, we are not much more advanced today.

The T2 chip installed in the iMac Pro (image iFixit)

Customers who go to the Apple Store or call Apple technical support are always instructed to reinstall macOS, but that doesn’t change anything. Following this, some have obtained a complete replacement of their Mac, or at least a change of motherboard. Likewise, that doesn’t fix anything and bugs usually end up coming back.

If not macOS or hardware, maybe it’s the environment? In fact, several accounts indicate that the crashes only appear when the Mac is connected to a device, in Thunderbolt 3 or USB-C. Connecting the computer to two external displays seems to increase the risk, but it isn’t systematic either. And then, some people suffered this bug when their Mac was not connected to anything, not even aware of it.

Is third party software responsible in this case? This is the fairly obvious answer from some Apple employees, but customers have made the effort to reinstall macOS and leave the basic configuration untouched and still have unexpected reboots. This bug occurs even during standby for some, while macOS was active for others or only when the Mac is in high demand. It seems impossible to find a single point common to all these cases, apart from the presence of the T2 chip.

This Mac affected by the bug unexpectedly restarted no less than ten times between 7 p.m. and 10 p.m.

The only thing that is certain is that these crashes are starting to seriously annoy the people concerned. And we understand them: this bug listed since 2018 can cause dozens of unexpected reboots per day. In the forums, everyone has their own trick: prevent the Mac from entering standby, cut PowerNap or even disable the automatic switch of graphics card on Macs that have this option. Nothing really works, however, and we’re still waiting for a real solution from Apple.

If you use a Mac with a T2 chip, have you noticed these unexpected restarts too? Feel free to add your testimony in the comments!


6 thoughts on “T2 chip still causes unexpected restarts for no known reason”

  1. yes, I have had this problem on my macbook pro. it occured while reconnecting an external drive to a hub plugged into thunderbolt 3. T2 chip. I restored my OS catalina 10.15.2 and issue has not re-occurred, fingers crossed. my machine info is:

    Model Name: MacBook Pro
    Model Identifier: MacBookPro15,1
    Processor Name: 6-Core Intel Core i7
    Processor Speed: 2.6 GHz
    Number of Processors: 1
    Total Number of Cores: 6
    L2 Cache (per Core): 256 KB
    L3 Cache: 9 MB
    Hyper-Threading Technology: Enabled
    Memory: 32 GB
    Boot ROM Version: 1037. (iBridge: 17.16.12551.0.0,0)
    Serial Number (system): C02X7314JGH6
    Hardware UUID: 54E3BE23-B087-5C6B-8E85-F079BC52C842

  2. I have a daily unexpected crash and restart message (kernel panic) that has been annoying me with my brand new 16″ MBP.
    Running Catalina 10.15.3, TB3-TB2 adapter for 27″ TB display, reset SMC & reset PRAM.
    Changed security settings (no filevault), energy settings (powernap off), etc.. that the Apple support said I needed to do.

    Now the only thing left to do is a OS reinstall…

    What a pain coming from a non T2 chip 2012 MBP….

  3. I have been having this problem for about a month now with a brand new MacBook Pro (2019) bought from Apple at the end of Jan 2020. Endless unwanted restarts always with that BAD MAGIC! Message afterwards. Endless discussions on the phone, with AppleCare techs, from Chilean Patagonia via Skype, nothing helps, and have been unable to reinstall Catalina due to sketchy internet connections here. This is the worst Apple experience ever, the Apple advisors are unable to tell me why this is happening, and just repeat a few of the same suggestions like a stuck record. Very, very discouraging after spending almost $4,000 US for this new MacBook Pro. And yes, for sure it has the dreaded T2 chip.

  4. I have a brand new Mac mini 2018. I started getting these reboots (3 so far) after I installed third party RAM and a Thunderbolt 3 enclosure with NVMe SSD. It only seems to happen at night when the Mini is sleeping.

  5. Had several crashes with a MacBook Pro 2019 15′.
    After a very long, exhausting period in which i was trying to resolve the problem with Apple’s team.
    After nothing helped, I reinstalled the MacOs (Mojave).
    for a month it seems to help, but now again it is coming back.
    I’m very disappointed from Apple. A premium computer (or premium a price tag) shouldn’t have this kind of problems,
    and if it does, i was expecting Apple to give it an appropriate answers and solutions. The last solution they gave me – send to to a repair.
    I have yet to see an evidence of anyone with this problem sending in their computer for a repair which actually solved the issue.
    What the hell is going on, Apple.

  6. This just had happenned to my laptop. Same issue. As I’m gettin to all this information is being happening for months and no body knows why. Surely someone had to set that Black Magic message, it can’t be in another way, can it?


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