If it's been sitting, I'd definitely get out the manual and "clean and oil" it. Perhaps some of the oil or lubricant has hardened a bit and not doing the job it was intended to do.
Also check to see if something (attachment or bobbin winder contraption or belt or screw) isn't rubbing or loose. Not familiar with that brand/model, so maybe it has to go back to the store? Let them check it out and see, when you're there, if other models also make that 'roar'.
Good luck.
PS: When maintained, those little FW's do hum so softly and lovingly. Love mine!