Make sure your feet are ALL the way up to the top of the pedals before you initiate manual braking (so you can feel your toes pushing up against the “lip” on top of the pedal).
The fulcrum point is high, so will not get full brake authority if your feet are not all the way up there. One foot still being slightly lower while braking is the most common cause I have seen of a consistently uneven brake temperature both taxi and landing. Generally you will be subconsciously compensating for the uneven braking with slight rudder pressure opposite the stronger foot, which tends to make it worse.
Easy to see from the jump seat, and easy to fix!