Moisture has caused a little short in between the contact under th keyboard.

I would recommend to open your phone and gently wipe any moisture under the keyboard..

1) Remove Battery
2) Remove 2 #6 torque screw from rear top of phone
3) Using a prying tool remove base of phone ( where the log of the phone company is
4) Remove 2 more #6 torque screws
5) Remove side chrome cover ( Snaps on)
6) Lever in between front and rear case and pry open gently
7) Wipe gently and re-mount in reverse order..
It should work