Sleep/Wake issue with 5K Retina
I Have just purchased an Apple iMac 5K Retina, 4Ghz and 16 GB of RAM. I am experiencing an intermittent warning, which suggests that the system has restarted from Sleep, for some reason. I have contacted Apple Service, who took over the system and gave it a thorough test. After the test and removing an external Disc, the problem seemed to have disappeared. However, this afternoon, it came back again. After closing the warning, the computer seems to operate as expected, with no obvious symptoms. i have originally been told that I can return the iMac if the error re-occurs, which it has. The system is not standard, so I probably would not get a replacement before Christmas, but having spent over £2000 on the equipment, I do not want a flawed product. I will also find the re-instatement to Factory settings a real ' ***'. Any advice from an expert would be much appreciated, before I ring Apple tomorrow. Should I try to return it or is it a trivial issue?
iMac with Retina 5K display, OS X Yosemite (10.10)