[miketwalker]

Could you possibly have your if loops in a certain order where if one's being pressed the next loop is overwriting your command output and setting the value back to 127 (neutral)?

For example, to show my logic:
if (button1) : pwm=255
if (button2): pwm=0
else: pwm = 127

In the above, even if button 1 is pressed your button 2 code is overriding that "255" command since the final value is essentially a 127 since button 2 isn't pressed.