external display issue

[mcjz]

I have an ASUS ProArt 246 display monitor which used to work great with my Macbook Pro 2.3 GHz 15" retina (Mavericks) connected via HDMI. That machine got stolen a couple weeks ago and I now have a replacement Macbook, the new generation 2.5 GHz with Yosemite. My ASUS display now intermittently goes blank on & off, flashes "no HDMI connection" and goes to green screen for short periods of time. It will work fine for several hours sometimes, then have a few episodes of this behaviour, totally random. The episodes can last for for about 20 minutes sometimes, then normality for a long time. I've had the logic board replaced, no difference. The machine is brand new. Another issue is the bluetooth connectivity seems unstable from time to time. Has anyone else seen this behaviour.. is it a Yosemite issue? Mike