Ok, returning my 2nd monitor - for four reasons:
1) Coil whine / buzzing coming out the back, near the onboard PSU. Not particularly loud, but can be heard in a quiet room when I have the brightness up. First monitor never had this.
2) When the monitor is in standby, I can hear a constant ticking noise near the PSU. Again this is not loud but does indicate some kind of issue.
3) Slight white screen flickering (full screen) when hovering the mouse over an active window, like an in game menu for example. Tried 4 different USB sticks - all formatted correctly - but the monitor will not recognize the latest (M-T9549GGAA-1006.2[BC89].img) firmware. Have tried 3rd party formatting tool.
4) Cracking/popping -this seems to come from two sources. One is the plastic as I can replicate the noise when, carefully, pinching the the back covering. The second comes from the power source. I ever had a "crack" approximately 2 hours after turning it off the other day.
I will carry on till I get a good unit, as I'm in love with this monitor.