Double Ought- Titanium, steel etc does not matter. The firing pin designed for THAT gun matters. The firing pin is held in place by a retainer- looks like your cousin lost the retainer. Gun uses a transfer bar system IIRC- hammer hit the bar, which hits the firing pin. Find a gunsmith, pay him to do what he doe for a living- it will be worth it.
While you are there, give him your pump gun. There could be a number of things causing fail-to-fire, none of which are truly identifiable at long range.
What we have heah is.... failure to communicate.