Something (piston) had to of hit that electrode to bend it that far. There may be a floating part trapped in the cylinder as old dog said, more than likely a valve cap or a piece of of a valve cap,
maybe a stray piece of metal/fastener got sucked down into the cylinder, but pretty unlikely.
Are you using the older style sodium valves? They like to break.
Its a PIA but at least you shut down early before more damage could happen.
Hmmm...interesting looking hair to the left of the plug, you been fooling around with the Mrs. on that table top?
