The contact owns a 2016 GMC Yukon. The contact stated while driving at various speeds, the vehicle would shake and vibrate. The cause of the failure was not determined. Also, the driver and passenger side retractable running boards would erroneously retract back and forth while driving, and on several occasions, while attempting to exit the vehicle the running board remained retracted causing the driver to fall to the ground and causing injuries to the driver's legs. The cause of the failures was not determined. The manufacturer and local dealer were not notified. The failure mileage was 60,000.