Two things I can think of:
First off, check the bolts that hold the latch in place. You'll have to pull back the plastic cover some to see, but shouldn't have to remove it fully. I've had both fail, which allowed the latch to loosten. My problem was more the latch acting up and not catching than squeaking, but it could be possible
Another is the rear shock mounts, though I would think they would make noise on bumps. I couldn't figure out where one of my squeaks was coming from until my RSM failed, and the shock was sticking through the carpet
Didn't really have a pattern to it making noise though, was more random than I'd have expected.