Maybe have to check the wheel speed sensor wave forms or digital patterns with a an oscilloscope. All tires the same size, wear and, inflation, no play in any the wheel hub bearing?

 If it happens in a level parking lot and I take hands off steering wheel and it kind of wants to go to one side while braking when that happens intermittently, then typically it's usually the front opposite side of the pull that is getting denied some braking because the signal is dropping out or not putting out a clean enough signal and the ECU thinks the wheel is skidding