iMac (Retina 5K, 27-inch, Late 2015) Randomly Restarts Without Errors

I had that feeling myself once. Saw the mythical 5 days uptime before two random freezes the next day.

This really puzzles me' why does it seem to be stable for quite a while and then restart several times per day for a while? I hope we can at least get a decent explanation when this is sorted, because living with a computer this hilariously unreliable really should warrant a good and thorough walk through when it gets fixed. ;-)

-KJ

My longest streak was 6 days - almost 7. The worst day was 3 random restarts. As of this week since Saturday there have been four random restarts. That would be nice to get Apple to come to my house and swap out the Logic Board - if of course that proves to be the issue.

That is the least they can do.

Yeah, everyone who has got the logic board replacement and has posted here has seen zero issues since the logic board was replaced––but getting Apple to that point is like pulling teeth. It's been a part time job just dealing with all the support issues.

I've been on the phone with Apple for the last few months now trying to isolate the problem with no luck. Thought it could be extensions, to bluetooth issues, to iPad Connectivity handover issues. So far the issue continues to persist. I spent close to 4k on this top of the line iMac and am beginning now after finding this for the first time to believe that this is a manufacturer flaw in the hardware and I want a replacement. I run my business from this and the random restarts cost me time and money. I've even removed the external bluetooth keypad with same continuing issues. Doesn't seem that Apple really knows what is going on and I've wasted countless hours on this with no resolution. It is a shame because the computer is great when it works, but I've never had a computer that spontaneously reboots like this. I am still paying for this but I may have to push this harder to get a resolution unless Apple can step up to the plate and offer me a real solution that isn't going to cost me any more time.

Backing up a step, one question I have for everyone is: have you ever had (or even heard of) random freeze-->restarts on other Apple computers? Part of the reason why I'm so quick to assume that we're all experiencing similar problems is that I've used Apple computers exclusively for 20+ years and have never had ANY product, desktop or laptop, exhibit anything like this behavior. Yes, I've had the occasional crash. That's to be expected. But in each of those cases, the computer would give me its little crash message upon restart (the "your computer had to shut down because of a problem, would you like to send a report to Apple?"-type message) and those instances were VERY few and far between.

With this freeze-->restart thing, the computer doesn't seem to really acknowledge that it is taking place--as pointed out in previous post of mine, there is a "Previous shutdown cause -128" buried in the boot record in the system log, but there's no record of any restart message or broken process at the time of freeze/restart. Nor, upon restart, does the computer give notice that it had to shut down/reboot because of a problem.

This something that has NEVER occurred for me on any other device, even sporadically, let alone the 3-6 times a day it happens on this machine. All of which is a big part of why I assume this is a problem that is somehow related to this generation of this specific machine, because it's a peculiar problem also happening to other users of this machine. But if this type of thing happens to other Macs, and I have just been lucky enough in my 20+ years and dozens of machines to have never encountered it, then I'd be more willing to re-examine that assumption. Any thoughts?

Hi Jon,

I've used Macs for 15 years and have NEVER seen a problem like this! I believe it is probably (hopefully) isolated to this generation/model of iMacs.

I am also currently very upset with Apple Support––I was promised two weeks ago that I would hear back from Apple's engineers on a solution last week, and it is Monday and, after leaving a voice mail with the senior advisor I've been speaking to on Thursday last week, still have heard nothing.

Apple needs to address this problem with the urgency it requires. Like so many here, my iMac is my work machine, not a $4,000+ plaything. Otherwise, I will need to consider other options for video editing workstations in the future.

Hi Jon,

I did have this happen to me on my late 2012 27" iMac as documented here (27" iMac randomly reboots) which seemed to just disappear as an issue after a while. At the time I had a suspicion that it was related to Time Machine as I was having immense difficulties with my External HD's being constantly randomly ejected or, even worse, completely wiped. I cannot remember what sequence of events or troubleshooting sorted the problem but it did go away by itself and the machine has been completely reliable since then.

This new iMac of mine was utterly unstable for the first 2 months and, ironically, since I found this thread (and others) I have only experienced the random reboot twice in the last 3-4 weeks.

So, maybe it is an iMac issue in general, and not necessarily the most recent 5K model.

Just wanted to report another case here: Random freeze, followed by a reboot, that produces no errors other than the log in the console: "Previous shutdown cause: -128".

Considering that this is happening to 5K iMacs, the most frustrating part is that Apple's customer service doesn't get these are used for work and that in many cases, leaving the computer for an unknown amount of days, for tests in the service center, means being unable to work or a big reduction in productivity by being forced to use a backup computer.

Since they have no idea what is causing it, they want us to lend them our computers for debugging, but each day they spend trying to figure out what is the problem, is money lost for us.

Right now my iMac is at the service center, but even if they claim to have solved the problem, by replacing some piece of hardware, I won't be using it for productivity any time soon, as I have lost the trust in their tech support and will instead run further test to verify that the rebooting indeed has stopped.

It is obvious this is an obscure, hard to detect problem and I get that it takes time to debug, but for a computer openly marketed for productivity, Apple has to simply accept that a small amount of their computers is defective and replace them.

Even if my iMac is still in the repair shop (this is the second time, for the very same issue), I'm already suffering the inevitable period of uncertainty, spending weeks nervous, hoping the issue was actually solved, if they refuse to replace the whole unit. I already had to wipe an external drive clean, because it got caught transferring data at full speed, by one of the iMac reboots.

I have owned iMacs before and we own several MacBooks, so I know how reliable Apple hardware can be. The question is if Apple will be up to its reputation when things go wrong. This experience has been very frustrating and will leave a big impact, one way or the other, of the brand, on me.

This is getting ridiculous, and I am beginning to lose my patience. Apple Support is either choosing to ignore me, or they're unwilling to perform a necessary hardware fix on my iMac 5k.

This severely diminishes my view of Apple in my mind––I'm a loyal Mac user for 15 years, and spent $4,000+ on my iMac 5k for work! The iMac did the random restarts twice this morning, five minutes apart––this is unacceptable for my workflow.

Apple, you NEED to address this issue now, or you stand to lose a customer.

Interesting. I got restarts back to back in the space of about 5 minutes this morning as well. This after I uninstalled the Ghostery Safari extension and it ran without reboots for about a week. Before that it had actually gone several days without a reboot.

I sent in more logs.

I reported earlier that my Late 2015 5K was rebooting without errors and mysteriously stopped doing it. Today, I realized that it stopped rebooting, etc. right after I removed Flash Player. I don't know if that was the fix or not. But, there it is!! I noticed Adobe put out an update today...

"The updated version, 22.0.0.209 for Windows, Mac OS X, Chrome, Internet Explorer and Edge, as well as 11.2.202.632 for Linux, replaces 22.0.0.192 and 11.2.202.626, respectively."

all from the "whatever it's worth department"!!

Reynolds Young

Arlington VA

Please be more careful before jumping into conclusions. Many of us have already discarded third party software as the source of the problem. I don't even install flash player.

Ensure you are indeed experiencing the same problem discussed in here, as this problem persists with clean reinstalls of the operating system.

It would be nice if it was an App - I think it is a deeper issue.

On my third Senior Adviser. Seems they are all on the ball for the first week and then they just pitter patter out. Haven't heard from my guy since last Tuesday - I think they figure we will all go away. I guess I will have to call Apple and get a fourth Senior Adviser...

I feel I am dealing with some Apple Knock off company and not with the real Apple Co. that I have heard so many good things about. They have got to have the worst customer service department of any company I have dealt with. The warranty appears to be completely worthless. The computer is a lemon and Apple seems to not want to address this. This is not a $199 Ipod - I spent over $2,000 on your product Apple - some have spend over $4,000 - we want this issue resolved.

My best guess is Apple has no idea why our machines restart, which would not be a good sign.

It's really ridiculous that when it appears that the logic board fix is the solution it all depends on which support person you talk to or which Apple Store you go to. By now enough "advisors" should be on the same page. I feel really lucky to have gotten the new logic board on my second visit to the service place without argument. Not sure still how that happened. I only talked with one advisor who thought it was the power supply and I just emailed the second advisor about the possible logic board fix I read about here, and when I went back to the service place they replaced it. Never heard back from the second advisor though. I hope this gets resolved soon by recall or logic board fixes.

Thank you for continuing to post in this topic! The rest of us need someone here who can continually say to Apple "Hey, the problem is hardware, not software, here's proof, and treat others with this issue like I was treated."

I went around the first Apple Advisor I was speaking to since I hadn't heard from him in over a week and got connected with another senior advisor. That was the necessary kick in the pants to get the engineers to finally tell me that...Google Chrome and Adobe Creative Cloud are at fault. Not the 10.11.5 update that bricked my machine.

At this stage, they're pointing fingers at anything non-Apple on my machine as the source of the problem without truly investigating a solution, it seems.

I have to uninstall these apps and see if the random restarts go away––however, I cannot do that until Friday since I need these apps and this computer to work on video editing projects for my job, restarts or no.

This means going through what should be another week plus of my work computer not functioning properly and delaying the necessary repairs.

This is the exact sort of advice given to others here and it didn't work, so I know with 100% certainty this won't fix the issue.

Can someone please replace the logic board in my machine already!