Get some WD40 and spray on the inside of the machine near the stitch length and reverse button area, I think it may only be stuck, put the stitch length on the longest stitch and when you have put the oil on move the stitch length dial back and forth rapidly and all being well it should pop out, if it does not then it it will be a shop repair.
Ken
drivewithken@blueyonder.co.uk
August 2008