I have read a few posts with complaining about strange sounds coming from the roof. Last week I noticed a knocking sound happening irregularly and difficult to isolate its location. Opening the sunroof the knocking was occurring from the front section of the roof rack off. Upon closer inspection a few mounting screws were missing and completely sheered off. That explained the knocking sound as the front leading section was loose from the side rails. A quick stop at the dealer fixed the problem and they were not sure if the sheered screws were due to over torquing, or vibration. Other than that, the a-pillar crackle still is apparent at higher speeds and I’m waiting for that fix during my next service. My Defender is used for towing an overland trailer and has the Expedition non aerodynamic package so at highway speeds the tunes, wind and tire noise drowns out any little annoying rattles, or crackles. 😁