It's a very rare event on 680 series guns.
If you remove the stock you'll know if it was a double discharge.

I always worry if older gun barrels have been tinkered with. Listening to all the mythology at my club makes me uncertain of their sanity.

When I've been involved with a similar situation, the cartridge maker couldn't help fast enough. In return for the barrels.

Out there doing it best I can.