Exploded view of Interarms/Mauser 9mm

[lfid]

yes, new oem Mauser mfg pin is very likely better choice than using standard P08 pin and likely much cheaper than a custom made pin and Lugerdoc price for new MP pin seems very reasonable

if you use a new MP pin or similiar copy, check that the flange sits flush to slide with the receiver pin flange recess and that the pin is at least as tight in the MP toggle as a P08 reference pin - ie about same amount of wobble for both pins in the toggle pin hole and also similar test for pin fit to receiver pin hole ( which should be tighter near perfect fit both sides receiver to the pin main body )

also check that flange diameter has some clearance with the diameter of the slide recess pin hole - ie should not be a tight fit - or about same clearance as P08 pin in a P08 slide

seems a P08 pin could also work, but you would lose some degree of safety as the larger diameter flange on end of the original MP pins provide some added assurance that the pin wont walk sideways during the recoil cycle

the later WW2 Mauser made lugers have a rear frame hump to provide similiar assurance of sideways pin walk control or worse yet the potential sideways walk and then flange end of pin grabs left frame rail on forward part of recoil cycle - as seems this grab must have happened somewhere earlier in time, perhaps from guns with very worn battered end of breechblock to the inside rear end of frame gun or overloaded/proofing ammo
most high usage worn weary military lugers (all non-MP) I have seen did have some degree of rear breechblock slap damage to the internal rear frame

other than yours here, I have never seen another case of a Mauser Parabellum 70s gun with a fractured pin
The example in my post above was for a WW2 mauser frame and receiver using a dwm breechblock/center link/rear toggle with unmarked P08 axle pin and likely broken by usage of cor-bon/heavy loaded ammo in this worn perhaps loose anyway mixture of mismatched mfg parts

so as far as I know, it is incorrect to say that this fractured pin problem is a known problem / Mauser factory fault. in fact, perhaps it is less likely with MP than older mfg lugers

good luck in fix quest !
Bill