For something that much of a safety issue, I would insist on them testing each wheelspeed sensor via oscilloscope pattern as well as swap in a new AdvanceTrac control unit for diagnostic purposes. Get Deysha to light a fire beneath their butts. I understand the difficult to duplicate and diagnose concerns being a tech myself, but for things safety related we check until we are certain it is fixed.
This x1000. Something that can potentially cause a fatal crash should really be looked into beyond the general "uh, we don't hear anything strange" kind of inspection. Get a hold of Deysha if you have to.