thanks everybody for the help but we found it and it was to simple to even put into words. After scrutinizing every inch of wire and every ground and every component of the ABS & TRACS system following a wiring diagram it turned out to be something simple. It looks as though somebody had been into the wires behind the dash (probably to do an a/c evap) and i guess the were too rough with the connector back there. One of the pins on the connector was disloged by 1.5mm (we measured it because we were shocked!). So when the car hit a bump it wiggled the connector just enough to lose signal to the LR wheel speed sensor.
I hope this helps anybody who may have this problem in the future

thanks again for the input