Thanks for everyone that posted up videos and tips on how to fix the rattling/ thumping from the tailgate. I added the washers the other day. Makes a huge difference. Tried two washers at first, trunk closed but u could tell it was popping up. Changed it to one washer hatch, it sits flush and no more noise. super easy cheap fix that we shouldn't have to do but its better than going to the dealership imo.
One of the fixes from kia is moving down the strike bar on hatch. They pop the welds off and move it down.plus add another washer. The problem is the hatch noise is from side to side movements. Go thicker with washer.
My 2019 has had the thump/thud sound over bigger bumps for the last few months and was driving me insane. Finally fixed it by adding a 1/16 custom rubber gasket from the hardware store (no washers) cut to the size of the hatch bumper.
This video is where I got the idea from. Also I thread the hatch stoppers to the red line (just above the small lines imprinted on the stoppers) Trunk has been silent for over 2 weeks now.
The latch assembly has too much play so it rattles. Some have found that wrapping strips of duct tape around the "D" that the latch latches to effectively removes that play. If you use too much tape, a hatch open warning appears on the dash so go incrementally. Here's a link with a pic... Fixing Trunk Thunk !! ....................