Macbook Pro 16 crashes on sleep when external screen plugged

I too was extremely frustrated by this (MBP would crash every time it went to sleep while connected to a dock) until I came across another thread here which fixed the issue for me and others. Go into System Preferences -> Notifications -> Do Not Disturb -> Turn on Do Not Disturb and check "When the display is sleeping." This will prevent the OS from showing notifications while your computer is sleeping, which is causing major problems when an external monitor is hooked up. Who wants this feature anyway. It's silly, and it's especially silly that it's causing people's computers to kernel panic.

The latest version of Catalina is 10.15.7 (19H15). I recommend that you apply all updates and revisit whether you can reproduce this problem afterward.

All of the same problem posters should originate their own new posts to avoid creating distractions in this thread through thread-jacking. The first and only support priority is to metmirr.

New version of macOS Catalina10.15.6 fixed this inconvenient problem. Updated our MacBooks guys, works for me :)

I am having the same problem since the the last update macOS 10.15.5, the only thing I have found to keep it from crashing when connected to an external monitor is to check "keep computer from sleeping when display is off" and leaving the lid of MacBook Pro 16" open, if I close the lid to use it in clamshell mode it crashes when it tries to go to sleep.

Hello metmirr,

Welcome to Apple Support Communities. It sounds like you're having trouble with your Mac while it's connected to an external monitor. I'd be happy to share information that may help.

Take a look at the steps here, and give those a try: If your Mac restarted because of a problem.

If those steps do not resolve the issue, please reply with whether or not this occurs when your monitor is disconnected.

Take care.

Same problem started 2 days ago with NEC monitor. Crashes every time it sleeps. Spent an hour with Apple today and in the end was left with "a fix is in progress" but did not know when. Tried solutions above with no improvement. Had this MBP 6 months without a problem, also running 10.15.5. I guess I will have to set for a long delay before sleeping and then unplug the monitor USB. Does not happen when disconnected.

Same problem here, 10.15.7, mbpro with Philips monitor.

Disabled notifications, we'll see.

Changing the settings to disable notifications while asleep seems to have resolved my issue.

Screen freeze resolved by using safe mode.

I have the same issue with my 16 and external monitor. Each time a few minutes after sleep I get the restart error. For now I stopped using the sleep function, but I am hoping apple will fix this. It used to happen once or twice a day with 10.15.4, now I am on 10.15.5 and it happens almost immediately every time computer goes to sleep so I am pretty sure it is sloppy Catalina code...

Same problem here.... MBP 16 (2019) crashes every time I put it to sleep closed with external Dell monitor (s2718d). Doesn't wake up computer or monitor with external keyboard. On opening mac the keyboard will be lit up with display dark and you have to do a hard reboot with the power button. Not the most inspiring way to get to know my new super-duper computer. What are people doing about this again? Is it the OS or the monitor drivers(no mac drivers for my monitor)?

U experience the same issue . MBP16 and Dell usb 27 unchaining monitor.

Also happens that in hot weather MacBook start to lag while connected to the monitor. Holds CPU above 70%

Once you disconnect the monitor , computer is back to normal.

Apple delivered today's macOS Catalina 10.5.6... Let's see if they fixed

I'm having same problem since like a month. At the beginning it happened every so often but now it happens every day. MDB 16'' connected to an external monitor vía hub USB-C --> HDMI with no other peripheral than the monitor itself.