Hey Tony
Anything is possible. The fellow that helped me with the engine rebuild( bearings, crank plate bolt mod, balance shaft rebalance, etc) is a retired Honda motorcycle tech who supposedly was that particular shops engine guy. Not to say mistakes happen.
When I spoke to him tonight about me findings, he wondered if maybe the bolts bottomed out right at the point they would reach their torque setting. So it might have not been noticeable. So I might investigate the other bolts to see if the length is a concern.
Or maybe that particular bolt wasn’t torqued…….?
And it worked itself loose to the point that the rocker shaft was moving and then putting stress on the bolt?
Just a thought