Experiencing intermittent shutdowns/power loss with a late 2015 5K iMac (i5 3.2ghz/M390/flash storage) Haven't been doing anything GPU or CPU intense, it's happened at random times, and even when it's sat at the login screen. It won't turn back on immediately, had to pull the power cable a couple of times and plug it back in to get it to power on. I've reset the SMC, checked and reseated the RAM, checked the power cable for damage, even used a different power outlet. Luckily it's covered with AppleCare (had the screen and logic board replaced in October 2017). From what I've read it's likely to be the PSU so just want to be sure there isn't anything else I can check before I lug it to the Apple Store?