With KitKat just released, this may be a little late, but we just discovered a bug in the binary library hwcomposer_viv.imx6.so.
We've been testing our new Nitrogen6 Max board that has dual LVDS and 4GiB of RAM, and noticed that when using dual displays, the second display doesn't refresh properly. Instead, it often displays something a few frames behind, and sometimes appears to
Either checking the box in Settings|Disable HW Overlays or renaming /system/lib/hw/hwcomposer_viv.imx6.so so that it won't be found fixes the issue, and both displays operate correctly.
Similarly, passing a kernel command-line argument of mem=2G allows things to operate properly.
It's just an educated guess, but this appears to be another form of the bug addressed here in the GStreamer plugins, where an allocation test is checking for <0 to mean failure instead of testing for -1.
We haven't yet tested KitKat on this board, but will soon.