Just got a pair of 4K UHD TVs for use as computer monitors, one for me one for my wife, we both have the same video card, EVGA Geforce GTX 950.
She is running MATE 1.14, I’m still using the original 1.12. I upgraded hers to 1.14 when I first setup her monitor thinking it might be a bit better for a “high dpi” display – actually the screen is so big it ends up ~96 dpi in 4K mode and looks great after a few minor tweaks – set dpi to 96, change to large mouse pointer, and add 2 points to all the default fonts.
I’ve stayed at 1.12 since I’ve not noticed any significant differences in 1.14 – which is probably a good thing for 1.14 
My problem is if I turn the monitor off I get no display when I turn it back on – set give the no HDMI input message when it comes on. My wife’d computer doesn’t have this issue.
I’ve all screensavers and display blanking off – if I don’t want ot be able to see the screen display when I look at it I’ll turn off the monitor – I hate is presumptive eco-saving-crap!
So my problem is when I turn my monitor off there is no display when I turn it back on 
I can get it back with CTRL-ALT F1, which will show a text login promt, and then CTRL-ALT-F7 to get the X display back and everything is fine until I power down the display again. Been through this many many cycles and my wife’s computer doesn’t have this issue. Same video cards and drivers, all system updates.
I did not have this problem running dual 1920x1200 ASUS monitors and an older Geforce 210 video card (different drivers).
Any ideas? If no one has any suggestions, I’ll upgrade to 1.14 and see if that is the fix, but if the issue is not 1.12 vs 1.14 I’d prefer to stay with 1.12 for the moment.