Having recently bought a new Niro 4 I like everyone else was instantly delighted with it, except for 2 annoying rattles!
The first turned out to be a pair of glasses in the holder by the sun visor (my fault) the second an annoying occasional rattle from the tailgate. After some investigation and extra grease around the main boot catch I have found 2 small rubber bump stops one either side of the tailgate. Appears these can be slightly unscrewed on a thread to give a tighter fit and my rattle has now gone!!
Still delighted with the car overall great build quality.
Faults and Technical chat for the Kia Niro