Posted a few times regarding this iMac before. Had a screen replacement/logic board replacement October 2017. Took the iMac in for repair again to the same Apple Store in the UK, March 2018 as it was losing power/turning off intermittently. Was told they had run stress tests for 4 hours and found no problems. They erased and re-installed the OS which seemed to have fixed the issue. However 3 weeks later the iMac has started losing power/turning off again, but it is also displaying pink graphical glitching during startup/shut down. I do have AppleCare however surely having to take it back after just 3 weeks is completely unacceptable?