OK so I haz Sadowsky Metro UV5. One day I noticed a kind of clicking sound, probably when putting the bass on a stand, such that I was shifting its position and had my ear close to the neck and headstock. It sounds like a small part that's loose and when I say rattle, it's fortunately not the sort that presents any noticeable noise or vibration when playing, but it's audible (not through the amp) any time you gently shake the bass. I can't find anything loose externally on the headstock, and I've tried applying gentle pressure on machine heads, string tree bar, etc., but the sound remains. I'm wondering if it could be coming from the truss rod or related parts. As I said I can't hear any noise while playing but I haven't done any serious studio work with the bass yet, and I'd hate to write this off as me being overly anal and OCD, only to have it crop up as a real problem when I least expect it. Any ideas, suggestions, etc?