Experienced it twice on different cars.

Happened on my (former) series 2, one bolt holding the base of the mirror went off.

Also happened to the elantra, parang napunit yung sleeves sa railings kaya nalaglag. Replace it immediately. It will affect the mirror if you close the door while the window is rolled down. Iingay yung pagsara at parang may mababasag sa loob.