I had to bring mine to the service center. They found that the latch on the driver's side was defective and replaced it. It works great now, I can close it with 1 finger now.
I'm having the same problem! It has been like this for a few months but recently it is much worse. I really need to slam the tailgate to get it to register.
Let me know if you figure something out!
I have a service appointment but it isn't until November. I'm hoping the will be able to come to...