Read something, can't remember where, that the sensor polarity was reversed--ie, instead of releasing brake pressure when an "incipient skid" was sensed, it would actually increase the pressure.

In other words, it wasn't an anti-skid sensor--it was a guaranteed-skid sensor.

In the most recent case,the work was done by NON-UAL Maintenance. However, it did pass all the required checks after the work was done.

Guess only: the maintenance manual (Airbus) doesn't have sufficient info or diagrams, or has a reversible cannon plug. Something that makes it possible for a guy to screw-up.