[Steinar]

I'm trying to figure out why the rear part of the breech block looks to have been ground down. Perhaps to make it go back even further?

So far back that if actually strikes the rear part of the frame + making the forward toggle link have a too sharp sharp angle and therefore cracking it against the breech block.
Perhaps it's more a question of bad gunsmithing skills rather than hot loads?
I notice what looks to be a Lahti barrel on it, many of them are ex-military pistols.. If the military 9mm rounds are hot in sweden, that could also be the nutcracker.
As Vern says, it's best to be cautious. Replacing the toggle would most likely fix it, but there could also be problems with the frame. Look, or make a gunsmith inspect the area where the receiver (=barrel extension..or 'slide') meets the frame (the cut near the takedown lever). Also the receiver itself.
It hurts me to suggest this.. but if you deactivate it, you can probably sell it for the price of a simular Luger. At least thats the case over on our side of the border.