After months of dealing with this issue, it still is not fixed. My machine is essentially useless, so I have not even restored it. The first step I had to do was decrypt the hard drive, so then I shortly thereafter did a fresh install because I am not supposed to use a decrypted hard drive anyway. I can't conduct web based meetings on a computer that could black out at any second... sometimes multiple times in a row.
I took my machine into the Apple Store 4 times (I think, maybe 3?) and they could not accept my videos of the issue as "evidence". They also said they could not reproduce the issue and needed clear steps on how to reproduce it. Obviously I can't give steps on a random issue.
Here's what my screen blackouts were blamed on (none of which fixed issue)
TRIP 1) Hard drive encryption - I decrypted, which took 24 hours
-Did not fix issue, so I installed the OS over my files
-Did not fix issue, so I deleted everything and did a fresh install, which is how it sits today. I only installed a few programs like Chrome (which was also blamed).
TRIP 2) Third party RAM / too much RAM (32GB installed) even though it worked from the day I got the machine and passed all tests - they kept the iMac for over a week and claimed they did extensive testing, console log says otherwise. (Maybe they didn't realize I can tell when the computer was turned on and off). I reinstalled the original Apple RAM
CALL A) Advised to do TimeSnoops and DataCaptures. I was in the middle of moving to a new location, completely new ISP, new Apple Airport AC... and since I was moving, I dropped it off to the AppleStore with the assurance that they would do extenive testing.
TRIP 3) Apparently the RAM not in the "factory" slots (even though it worked fine without error).. so they said they swapped the slots around and "extensively" tested it again. They were supposed to also do TimeSnoops and DataCaptures for Apple Support during their extensive testing. Console logs showed the computer was only on for 2 hours during the ~5 days they had it. They said they could not reproduce the issue, and blamed it on the "environment" at my home. I was upset and didn't even notice the new scratch on the iMac base at first. I got the scratch notated on my account. As I have lugged this iMac around to Apple Store so much, the box handle even broke/snapped off. Luckily they iMac did not drop/break!
CALL B and on) Cannot be environmental issue because I am now in a completely new location, with a completely new ISP, wireless router (Airport with AC wireless), etc. I never bought that argument in the first place.
-Now they want more timesnoops and datacaptures. I comply.
-Chrome, one of the only programs I have installed, is blamed as culprit.
-I uninstall Chrome and avoid using it. Issue still occurs
-More TimeSnoops and DataCaptures
-They could not accept videos in the past, but now they want video evidence. My old videos weren't enough. They wanted videos of it happening under certain conditions like low ambient light, etc. I comply.
TRIP 4) After moving, I am in a location without an AppleStore nearby. I just dropped my iMac off to an authorized repair center.. and apparently they are taking a shot at replacing the screen, led backlight, and power supply. I admit I am concerned given that there are numerous posts pointing to these components plus video cards, logic boards, etc being replaced without a fix. Supposedly they are replacing the scratched "foot stand" part as well.
I also sent timesnoops of wifi/network issues and bluetooth dropout issues with apple mouse and keyboard. I'm not sure if they are replacing the wifi module and/or bluetooth module... or if I have to go through even more troubleshooting steps for these annoying but less debilitating conditions (e.g. I can plug it into ethernet, but having a cord stretch across the room and up the back of the desk sort of defeats the point of having an "all in one" that looks nice sitting on your desk).
Overall, I am shocked at how terrible this "AppleCare" has been after reading about other people's great experiences. I have lots of Apple Products (laptops, iPads, iPhone, AppleTVs, etc), and had been thinking about getting more. This experience really has me really opening my eyes to other alternatives. I had a DELL XPS with warranty that had issues and was repaired within a week... by someone who came to my home to replace parts!
Months of lost productivity on my main "desktop" is just unacceptable. Can I get by with my laptop and iPad? sure... but the whole reason to have a desktop with a huge screen is because it makes me more productive.
Just wanted to share my experience. Overall I've probably spent at least 30-40 hours of uncompensated time trying to document and fix this issue for Apple. What a waste.