NCHacker had this code:
else if(digitalRead(buttonPin02) == HIGH)
but what else could buttonPin02 be at this point?
Replace that code with:
else
Because buttons are read more than once, I suppose there is a minuscule chance that a button is read in one state at one time and in another state at another time. It would be better at the beginning to read each button and save its state, or even read the entire port and save the value of these two buttons. Then there would zero chance of a value changing while the decision process is going on.