Screen Artefacts Shutdown Sierra MacOS

① memo 20170329 ~ Screen Artefacts Shutdown Sierra MacOS ~ Screen artefacts on shutdown of the Sierra macOS (10.12.1 to 3) on iMac 27″ 5K Late 2015 – Note the artefacts vary greatly (in color and shape) every time this issue occurs. Apple Community discussion . Problem exist for some 6 months now , whether update 4 helps is unknown yet – Apple is silent on this.