Hi all, Yet another sleep/wake issues thread. It seemed the 2014 5K iMac had a tonne of issues which have now been rectified but they're back with a vengeance on my 2015 model: USB devices lose power (stop charging) after the iMac has been in sleep mode for some time The iMac will wake randomly during the night after this happens, and the USB devices become powered again* When waking from sleep the bluetooth keyboard and mouse are sometimes unresponsive When waking from sleep there is often a white square, about an inch high and an inch wide, of graphics distortion in the top left of the screen When waking from sleep the system is unable to connect to the internet, despite it showing as connected, until Wi-Fi is turned off and then on again This has only happened recently, about a couple of weeks after updating to 10.11.4. I've tried an SMC reset to no avail. I've tried removing USB devices but the wake issues still persist. The system runs fine once it's awake or has just been booted up. Has anyone else experienced these issues? Doing as much as possible myself before lugging this humongous thing on the tube to the Genius Bar... Update: I tried running Apple Diagnostics but the screen just goes black except for a small grey square. I then tried the online version of Apple Diagnostics, which would boot, and it found no issues. Hmm... *I know this because I have been woken a couple of times in the night from three charging iDevices making the "I'm now charging!" chirp all at once.