Here's the Nokia X3-02 Volume +(up)and Volume -(down) and side lock button switches connection tracks. This may help for your jumper wire needs in case if the button switches failed to work or having problem like: the terminal solder pads of the switches is damaged, the flex connection on the switches is already cut off.
Just refer to the solution below and carefully observe each of the button switches connection.
Just in the left side edge of the flex board, you can see the open spots where you can apply a solder for the jumper wire. This may help if the flex ribbon connection to the button switches is already cut or damaged.
Now, if seems that the flex is okay and the volume control and lock button switch already been check or replace but still doesn't work., the possible problem may lies on the keypad filter IC, replacing it will only fix the problem.. See here for the Nokia X3-02 keypad problem and filter IC solution, this will also help for the volume up/down and lock key problem.