I know this is an old thread, but resurfacing in case anyone has some info. I've seen a lot of threads on stuck hatches or replacing the lock mechanism but not for this issue specifically.
As the OP mentions, the rear hatch lock cylinder has broken loose from the plastic nuts which are attached to the hatch itself. The lock cylinder no longer has a way to be held in place. Has anyone else ran into this issue and what did you do to address it?