I second the suggestion to replace the gas strut for the rear liftgate. As the weather starts to turn colder it will start to support even less weight so you may as well replace it now while it at least still opens fully.

-Rod

 

Common problem on any vehicle with a liftgate. In your case the power operator side is fine but the gas support strut is shot. I've had that done once under the warranty, on my Durango, and the one on our Honda minivan died too. Not a terribly expensive repair and probably something you can have done cheaper at your neighborhood mechanic if you are out of warranty.

 

It's an easy repair for even a beginner DIY'er too. Sometimes no tools are required, but even when tools are needed, it would typically be possible to do with something as simple as a fingernail file or small flatblade screwdriver.

-Rod