Outside Side Mirror Vibrating or Shaking - Driver's Side

Mitsubishi » Outlander » 2013-____
Problem Description

I have a Mitsubishi RVR 2014 model purchased brand new. I have been using it every day since I got it and loving it. 

 

Recently I just noticed some side mirror vibration (driver's side) when I'm driving on high speed or even some semi-rough roads. Comparing the vibration to the passenger side, driver's side is worse. 

 

I have tried to tighten the screws attached to the body, screws below the mirror assembly and the screws behind the mirror (gimbal part) but I still experience the issue. I have found that driver's side has more tightened adjustments than the passenger side but still having this issue. 

 

I'm really wanting to know what could be causing this and how this can be resolved. Last thing that I have not tried is replacing the whole assembly but I'll leave that as last of option as it would cost me a lot that a simple fix (hopefully) will get this resolved. 

 

* btw, dealership has checked it and closed the case as "nornal" aka no trouble found scenario. 

 I would appreciate help on this! thanks