RE: UP3214Q/UP2414Q - 1/2 screen issue and/or No picture after powering off, then on
This is a byproduct of how MST works, or how the videocard deals with MST and lower resolutions.
To work around it, tell the monitor to disable DP1.2. Then you will get proper scaling. You will lose 60hz at 2160p, but 1920x1200 and lower will get 60 hz and will be scaled by the monitor. (On my system I cannot get 60 hz at 2560x1440 - probably a driver limitation of NVIDIA + Windows).