I have a 2015 LT Cruze with a side mirror issue. The driver's side mirror GLASS moves / vibrartes when going over 70 mph causing objects behind me to become blurry. The glass just moves, not the whole mirror assembly. I have had the mirror replaced twice now under warranty. The dealership refuses to do anything about it saying they contacted GM and that is just how they are made according to them. Bunch of BS. Any ideas on what could be causing the problem? Bought the car used with 7K miles on it. Under 20K miles now.