Chainsaws

555 Clutch Cover keeps coming off -- I recently purchased a 555XP with autotune. I love the autotune but the design of the clutch cover seems to be faulty. In the times I have used it, the clutch cover has come off nearly every time, not after hours but in less time than a tankful. It throws the chain every time, taking an hour to file off the burrs before I can resume. The bar tightener has broken twice and now the pin that the cover attaches to has broken or fallen into the body. Is there a design flaw? Is there a service bulletin?