o.k listen up.
if you change keypad flex and lcd and still same problem...
it can be 2 problems .
software or hardware from main board.
there is a little crystal IC near mainboard flex conector , rehot it with some flux ... if doesnt help , remove it and make jumper like in this pic.
if doesnt help you need to repair pds and full flash.
my problem got fixed with this jupmer 100% .
you can start with soft if you like ....
good luck