hi sifu2,my wife's s4 LTE 32gb is having issue with its display timeout. it doesn't turn off the screen after being left unattended.

-set for 15 seconds, at 15 the display doesnt dim at all.
-turn on or off smart stay (or any other smart features) still the same
-check developer mode, already turn off-still the same.
-already google,some suggest to do hard reset (seriously?)

last option, restart the phone then it will be okay. BUT, it will happen again some time after that. anyone in here having the same problem?
something to do with firmware or hardware.that s4 has been updated to the latest firmware.