if you have a problem Along with the trackpad try this solution:
1: replace trackpad
2: sometimes touch screen creates a problem so replace LCD
3: reflow or replace keypad connector
if still not work
4: Turn on the phone Along with an attached keypad and make a short circuit between the ground and the L1904 for 1 second (I am using tweezer) * the phone will turns off* remowe the battery and put it back to turn on the phone.
This solution it work for me on 100%