Rear Haych Subaru Tribeca

The rear hatch on my 2008 Subaru Tribeca makes a very serious rattle whenever you hit any kind of bump. I have had the dealer look at it several times and for a short period of time they managed to tighted it down but it slowly returned to the same problem. Subaru admits they had this issue with several hundred Tribeca's but yet they do not appear to have any answers or really any concern in fiting the problem. My concern is that it may be a safety hazard as the dealer tells me the hatch is not closed properly and you can see light through one side of the hatch. Will this lead to the hatch popping open in the event of a rear end collision?