Don't overlook attachments! Rests, sights, quivers, etc. I had a metallic thump , turned out to be the sight. It is a micro-adjust sight and when you tighten the allen screws ,you need to snug up the knobs also (just enough to take the slack out ) ,cause they will make noise.
Best way iv'e found is to hold bow in one hand and tap along the riser with the palm of your other hand. This will isolate the component that is the culprit.