Default Touch Key Light Duration Problem

I have a big problem with Touch Key Light Duration setting on my Samsung Galaxy Mega 6.3 (GT-I9205). Running by JB (Jelly Bean 4.2.2).

my real problem is..when i set to 1.5 seconds it's work but sometime its not work properly..its keep light on instead of 1.5 second or 6 second period end..why this happen? ive no problem with the light off key..my problem only when wait the touch key light goes off within the time period that ive already set.

For your infomation..i already root my device and this problem come when ive install Wifi Inspector, Wifikill & dSploit apps.