2004 YAMAHA FZ6 Power Train Problems

Front drive shaft, chain sprocket ‘Nut/lock washer’ has came loose and fell off on the highway. Could have locked the chain around the wheel and cause a major crash, also could have severely damaged the engine casing. It damaged the rear swing arm and a piece piece near the stater. I replaced the nut & locking washer tab, exact replacement only To have the same issue just I didn’t allow it to spin off since I was aware of this happening. I replaced the second one with a different style but same locking washer tab same issue it comes loose within 8 to 10miles. The nut is torqued to spec as stated by Yamaha. Iv reached out to several places including Yamaha and cannot seem to find a solution. Iv joined motorcycle forums and read people with same issue I’m having and wow am I lucky one. But they have...