10.12.4 display sleep bug

Thanks for that workaround. My problem with that suggestion is I know me and I would either forget to turn off both external displays or get really annoyed with having to turn on the monitors every time.

I have this same issue with 10.12.4 on 2 identical setups, one at home and one at work; iMac 5k i7 and Dell P2715Q. I reset NVRAM and SMC on one and the problem went away and on the other the same sequence did not work?

I am really annoyed, I buy Mac's because I need to work, they are meant to work and they are do not behave like PC's. Of course this happens when I have multiple deadlines approaching ...

Apple please fix this!

OK, I seem to have fixed the issue, at least for me. I thought I had done this originally but I must have done it incorrectly (or maybe you have to do it more than once) but I reset the NVRAM and SMC (in that order) again and all my monitors seem to wake up normally including the main iMac display. I know others have stated that they tried this with no success but for the moment it seems to have worked for me. I'll keep a close eye on this to see if the problem resurfaces and report back if it happens again.

I retried resetting the NVRAM and SMC on my iMac. At first I thought maybe that did the trick, but even thought the main iMac screen has correctly resumed from sleep a few times, most of the time it does not. When this occurs on my system, occasionally the secondary Dell screen will wake up, and I can reset the Mac from the menu on that screen. Other times the screen will wake up, but no menu is displayed (only the mouse pointer). On other occasions neither screen will wake up, but I know the Mac is not hung up because the Caps Lock key still responds. So it is kind of random.

I tried using an old Acer X203W screen with a DVI to DisplayPort adapter, plugged into the same port on my iMac, instead of the 4K Dell P2715Q. So far I have NOT had the problem, the iMac and Acer screens wake up every time. When I switch back to the 4K Dell, or use the Acer and the Dell, then problem is back.

I updated my MacBook (mid 2011) to 10.12.4, with Dell P2715Q attached as the secondary screen (although obviously not running at 4K). I cannot duplicate this issue on my MacBook Air with either the Dell or Acer screens, it works every time. At least in my case, it only occurs on my iMac 5K + 4K Dell P2715Q.

So much for that. It worked for me the first 2 times I tried to come out of power saver but when I got home tonight it did it again and I had to reboot the iMac to recover. And I had such high hopes. Is there any chance that anyone from Apple is monitoring this forum?

Adding to this thread... I have been having issues with my iMac 5K since I got it, not going to say it is Apple or the iMac's fault in total. I installed 64GB of ram and then found that one of the chips was bad after hours and hours of troubleshooting and re-installing Sierra twice.

Now I am at this point, I changed to using to Thunderbolt Hub's one is the CalDigit and the other is an OWC and everything was working fine till I did updates to 10.12.4 and then whenever I would come back to my desk shake the mouse or hit enter on the keyboard the iMac would come on display my desktop for a second then go off and come back on once along with my two external 4K LG Monitors and then while the two LG monitors stay on the iMac goes off and doesn't come back on till I do a reboot.

I have disconnected everything and the iMac works as it should so it seems to be a thunderbolt, external monitors issues or something along those lines. I see a lot of people have removed Duet, honestly I never installed it or use it... unless it comes with the iMac or Sierra and I just have not seen where to delete it.

I have reset SMC and NVRAM and changed around the LG monitors and how they are connected with no help. I will set the first two times out of sleep right after I reset the SMC and NVRAM it worked and I thought I was in the clear of the issue but it came back the evening when I got home from work. I have pretty much tried everything everyone has suggested or have tried with no success. I almost want to go back to Time Machine and go back to before the update and see if it fixes things until there is a fix to this new update.

Hopefully someone sees this and fixes it in the next update.

I have been turning off my second monitor before the iMac display goes to sleep and that seems to avoid the display bug. However I forgot to turn off the second monitor earlier today so I got the black screen of death. I was able through a few power cycles of the Dell monitor to get the lock screen login to show up on it. Once I logged in, it became the only display so I got the desktop and dock back. When I looked at the display setting under system settings it only shows the Dell monitor. When I look at the system information (from About This Mac) under Graphics/Display it only show the DELL P2715Q as the only display. So for some reason, the built-in iMac display is not recognized by the running system. Since I don't know of a way to kick the monitor from the command prompt, I will probably have to reboot the system to gain back the iMac monitor.

I will try shutting off my two LG monitors in the morning before I leave to see if that helps when I come back home after work. I can tell everyone else this about what I have;

- MacBook Pro, Late 2013 - fully updated, connected to a Dell 24" Monitor (1080p) with no issues.

- MacBook Pro, Early 2015 - fully updated, has been connected to 1 of the 2 LG 4K monitors without issues.

- iMac 27" (Late 2013) - fully updated, has been connected to an Apple Cinema Display (24") and Dell 24" without issues... ever.

- MacBook Air (Mid 2013) - fully updated, has no issues connected to pretty much any monitor I try.

I know I have too many computers, I also have Mac Mini's and they are hooked up to some Dell 4K's but since none of them are new, they only run at 1080p but do so without issues.

So it seems that this issue for my case is isolated to the iMac 27" 5K and Thunderbolt Displays or Thunderbolt Hubs + Displays...

I also received a phone call from Apple regarding this issue, and I have sent them the sysdiagnose file and requested info. I am very impressed with their attention to this problem, they are certainly working toward a resolution. I'll post again if I hear any news.

Same issue with iMac i7 with 5K display and 10.12.4 with 2 external 2560x1440 monitors attached via Thunderbolt to DisplayPort cables - Acer B326HUL and Acer K272HUL. No HDMI adapters involved with the iMac.

Since the Acer monitors are shared with other systems (the monitors have multiple inputs so the other systems connect to the monitors via HDMI), I do not have the luxury of turning them off when the iMac sleeps so I have had to disable turning off the displays in Energy Saver.

This is a very disappointing regression!

Just spoke to Apple support... They suggested resetting the SMC and (wait for it) reinstalling the entire MacOS (although they didn't ask me to erase and reformat the disk the way a certain competitor would)!

Nope. Not going there. Just bought the machine a few months ago and I'm not going to kill a day doing that. I bought this machine because I was having display problems with the external monitors on my old iMac.

We did the SMC reset and that seems to have fixed it - did a quick test with a 1 minute timeout on the Power Saver and the iMac screen came back. Set it to 15 minutes and I'll find out later today whether that makes any difference.

I think the SMC reset is only a temporary fix. I tried that yesterday and things seemed to be fixed. The computer also woke up this morning just fine. I then did some other work, can back and the computer was back to the internal display not waking (the external Dell monitor does wake).

Clearly something in the 10.12.4 update broke the way Power Saver handles "wake up" when you have 4K or WQHD external monitors plugged in. Resetting SMC every week or so is a pretty lame solution. Do we all have to go back to unplugging our computers to save power when we're not using them since that has the side-effect of resetting SMC.

It's kind of like Apple assumes that if you have a 5K iMac, you don't need to plug in external monitors. Well, we do. A lot of us do. So please fix this.

These are the facts I have so far on this issue. Its possible some of them only apply to my system.

1) Apple is aware of the problem. I have spoken to them and they are working on the issue as others also reported. It seems they are trying to gather system diagnostics of iMacs in their broken states. I have no idea how much progress they've made but I do know they're still trying to gather as much as info as they can on the issue. I was able to provide them with such a diagnostics file while my iMac screen would not turn on.

2) The problem is intermittent. I have seen it fail in just 30 seconds. I’ve also seen it not fail for over a day with several successful wake ups.

3) When the iMac screen fails to wake up, sometimes the external monitor comes on, sometimes it doesn’t. I have had instances where the iMac screen does not wake up but the external monitor does. But I’ve also had instances where neither turned on but I know the system was actually awake.

2) Resetting NVRAM/SMC doesn’t help. Though it may be a very short term fix. Hard to tell due to the intermittent nature of the issue.

3) Turning off external monitor before going to sleep is a workaround. Then turn it back on after wake up. Of course, unplugging external monitor is also a workaround.

4) The issue definitely started right after updating to macOS 10.12.4.

5) I did attempt a fresh install on my iMac and then went straight to 10.12.4 without installing any other software or even logging into iCloud. The issue still occurred.