The most likely culprit is a ferrule (even on a graphite rod). With all the pieces together there will be enough momentum to force a hinge on the part that is not perfectly joined. As JC recommends, put some paraffin on the joints and see what happens. If you feel the problem with no reel, perhaps it is the click of the locking ring. If you feel it with the reel perhaps the click is between the reel seat and the handle, where the reel seat meets the reel, or is the spool clicking on the shaft. Try with a different reel in that case, to see what happens. Good luck.