My iMac 27" 5K late 2015 has pink / magenta edges too. Last year I spent spent 675 Euros on having Apple Service provider change the logic Board because this 3500 Euro machine suddenly crashed several times a day.
I've had many Screens in my life, but I have never experienced this problem before. No have I ever seen this problem at any people I know, but I don't know anyone with an iMac, so I guess that's why.
Premium brands should help their customers with unacceptable quality problems regardless of official guarantees.
Miele once fixed my 6 year old washing machine because such a things should not happen on a Miele.
BMW once fixed my engine outside the guarantee period with the same argument. That should not break on a BMW.
Mercedes did it last year on my car seats with the very same argument.
I guess this is how the germans treats their customers and protect their brand reputation. I always buy Miele and never even consider another brand. I loved my iMac...before it turned pink.
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