Hatchback/liftgate problems of the 2006 Jeep Grand Cherokee

To whom it may concern: this morning I went outside to my 2006 Jeep Grand Cherokee limited, to pack it up for the day. I opened the back lift gate and began to load items. As I was loading stuff, the lift gate came crashing down on the top of my head, with no resistance. It hit so hard that for a moment, I was unaware of what had just happened. I tried to lift it off of myself, and it bounced back off my head again. I immediately got myself into the house to seek help. The pain was unbearable and I had tingling in the right side of my face and neck, and burning and throbbing pain in my head and right ear. I was immediately rushed to the dr's office and was told that I have a contusion, with bleeding in the muscle and symptoms similar to a concussion. I did not lose consciousness, but am suffering all symptoms. I was told to keep ice on the area and take tylenol for the pain. I need to be kept under observation for the next 24 hrs by my family. My father has come to the assumption that with it being 8 degrees outside, that the pistons were lacking or contained frozen fluid, which causes them to not work properly. This is a major issue, not only to me, but to others. This should not be happening regardless of temperature. I am thankful that no children were standing next to me, as it would have probably created a fatality with the weight and speed of the gate crashing. I have had to have the front hood piston replaced for the same problem, but never even thought of the back lift gate being an issue. I can tell you this is my second SUV and I never had this issue before with my other SUV, not even in temperature below zero. Please address this issue as soon as possible before someone else gets hurt, as most people are unaware of this issue, just like I was. I have only had this Jeep for a little over a month and it has been nothing but problems technically. Now that I have gotten those fixed, I physically get injured by it.