Shooting UK: problems with AYA No2

I have owned and used an AYA No2 single trigger for years but recently it's been playing up.

Firstly it failed to fire at all. A gunsmith found the cause to be a broken hammer. He said he had to order a piece and machine it to fit the gun. Is this correct or should the spare part fit straight into the gun?

I had the gun fixed and used it for a while then it played up again. It would either eject both cartridges even though only 1 was spent or it wouldn't fire the second barrel. The gunsmith said it needed looking at and the screws inside tightening up, which I had done.

The very next time I had the gun out (shooting pigeons today) it broke again. Both cartridges in the gun have been spent but the barrels will not break to eject the spent cases. The lever moves across ok but the barrels will not budge. I've noticed also that the automatic safety appears to have stopped working.

Does anyone know what the problem may be?

Thanks for any help or advice you can offer!

Lee.