Sounds like rocks rolling around trunk

[smfic]

So for almost a year I've been complaining to the dealers about what sounded like rocks/pebbles rolling around in my trunk when I stopped, accelerated, turned, etc. Basically all the time except cruising.
So long story short, if you get what sounds like pebbles rolling around, have them check the amp in the trunk. All the screws had worked loose and were rolling around.
Took the dealer 2 days and a weekend to figure it out.