Here in the states, (no idea where you're from) there are several that can do a good job and from prior inquiries the cost is about 650 USD. Plus ammo.
If yours shot well before perhaps the barrels are loose from broken solder joints? Hold the detached barrels by the breech end and tap the front end with a plastic handle of a screw driver. They should ring like a bell. If it's a kind of dull sound they're loose.
Are you using the same lot number of powder for the loads or a different powder? Have you done anything different with the brand of ammo if you aren't loading your own?