not easy to determine problem,if you dont have techno skills its best to leave it to the pro but if you wanna take a chance you can start at hook to see if there is cotton stuck around or insde outer and inner part of hook,from there you have to try and eliminate areas by seperating the different section of working mechanism from needle bar back to handwheel.this machine is nice to work on as panels are easily removed ,you can also try and spray with good penetrating oil to loosen parts while moving handwheel back and fro.not much to go on without seeing machine but if you patience you may find problem area.good hunting
johan
March 2013