If I understand properly, when you try to close the rear hatch, it engages with the latch, but does not close all the way - right? Does it ever close properly? Might this be an alignment issue with the latch mechanism?
I have another vehicle (non-GM sedan) which seems to have similar issues with the trunk latch not releasing once opened. The latch seems to close once the trunk it open ... and hence ... when i try to close the trunk, it bounces back in my hand, since the latch is closed (secure). It seems to be tempermental. Does that sound like a similar situation?
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Steven2001 Intimidator Coupe, 19K miles