For past two-three days I am experiencing this problem. Touch sensor just randomly stops working. Top side of the screen is very very difficult to control, sometimes even impossible. Sometimes it feels like sensor recognizes multiple touches at the same time which results random pages or menus opening and closing.
After short usage with screen up or after long downtime (like when I go to sleep) I'm not able to use sensor at all. I cannot shut down the alarm clock, I cannot answer the calls. I still can use the power button tho.
Now what is the most retarded is that nearly all that vanishes after phone reboot. The only thing that remains is that top side of the screen is still quite difficult to control. For example I cannot open that top slide-bar comfortably. I have to slowly move my finger over the screen in order to do so.
Custom ROM: Cyanogen 11-20140702-nightly
sdcard partition type: FAT32
bootloader version: 2.14
Custom recovery: TWRP 18.104.22.168
P.S.: tried to re-insall ROM did not help. Phone havent been damaged by any means recently.