Just for those reading this, the washer is a Belleville type that is cup shaped. The concave side goes toward the shaft the convex side toward the bolt head. If put on upside down the washer is just along for the ride and secures nothing.All, this is a delayed update. To last years issue but had to make sure the fix lasted.
So, I took the advise to replace the bolt and used fresh supply of locktite. I have put many hrs on since the new bolt and it’s held up no problems since.
Thanks for all your experience and time.
Mr G.