just sharing my experience: i updated to zvd, back to zvc, to cm11, back to zv7 and ota'd all the way back to zvd and my knock on still worked, it is now broken after i flashed the white lines fix after flashing the tmobile stock rom by novembre5. tried every fix in this thread and still no fix. knock off works flawlessly. im sure if i went back to zv7 and took all the ota's again ittl work but i need this rom to use my tmobile service.
try 3845#*modelnumber# eg: 3845#*800# change model number 800 with your phones model number, then tap on "Settings" and scroll down to "Update Touch Firmware"