I had the same thing happen to me a few weeks ago, but I KNEW the needle piece was there. I took it in, and was so concerned that I wouldn't have my machine for 4 to 6 weeks, like they told me their back log is. I thought I'd have to buy a second machine (which I'd love to do anyway, but w/ $$$ being tight right now, that won't happen). Well, thankfully, the woman just kind of shook it (gently, very gently, but I never would have done that!!!!!), and the needle piece came right out, and the thunking was gone!! And the cost: $000000
That's my kind of repair! Woo hoo!!!