Honda eb5000- broken valve, cracked valve assembly, etc

I was given a broken Honda Eb5000 from a client yesterday. There was something stopping the piston from reaching top dead center.

I pulled off the valve assembly and found the flat disc shaped part of the exhaust valve sitting on top of the piston. There were metal shavings in there that seem to have only come from the valve.

The cylinder looks clean otherwise, with no scarring. The valve assembly also is cracked on the inside around the exhaust valve.

Is this something that has happened to anyone before and should I replace it? I kinda want the generator, but I don't know how it happened, and don't want to put money into it to have it just fail again.

Any help is appreciated. I'm sort of noobish, but also decently mechanically inclined.