sound like a dry or damaged bobbin case,try put drop of oil between bobbin case and hook area,also stopper should be approx ,2 - ,3mm away from bobbin case,just enough for thread to pass thru.if oil does not help check for dirt on working area or replace bobbin case.worry is the rattling noise that could mean a seized or partly seized gear drive or damaged gears.gonna have to either try strip down or take it to techno
johan
November 2012