I had this issue when the Algonquins first came out. I figured out that it was a wire hitting/rattling one the wires inside. I zipped tied the wires to one of the braces and the problem went away. I also had another problem with one of them in a sence that the port's screen rattled. I determined this because I was able to move the screen with no resistance. Axiom sent me a new one and problem was fixed. So, check both (wires and port screen) to see if any of these are causing the issue. My Algonquins are problem free now and have had them for aboutg 2 years.