I have the 19 speaker HK system in my 21 Ram sport. Recently I’ve been noticing a rattle coming from the back left window area. You can only hear it when the bass hits. You can hear it on volume 9 and higher. I haven’t ever gone over 18 volume. When I bought the truck I never had any issues. It’s been 5 months since I’ve had it. Any idea what this might be? Or how I can fix this issue?