w850i backlight problem

hi i just flashed my w850i with W850_R1KG001_MAIN_GENERIC_CY_RED52.mbn using Setool2Lite v1.11 and also unlocked it

i dont know if it done it before as i flashed and unlocked as soon as i got the phone but now the backlight keeps going off but if you goto brightness turn it to 90% it comes back on and goes fine but then goes a little dull and off again after a while

any ideas why my phone is doing this?

also just to note

i think i might of messed the gdfs up a little as i pressed the wrong button at first

could this be the reason?