[John Sabato]

As you can see in this blueprint extract (Image 1), The area you describe is dimensioned as 1.3mm. it is the only dimension I see on this blueprint that is this value.

From the blueprint table the tolerance for this dimension is 0.1mm, (which was corrected from the previous tolerance of 0.05mm (image 2) which has been crossed out.)

0.1 millimeters is 0.003937 inches.
0.05mm is 0.0019685 inches.

I think that you have correctly diagnosed your problem as the extractor stops are excessively worn by constant hammering of the firing cycle (after being reduced in size by material removal during refinishing).

this gun is obviously a shooter class gun, so I wouldn't waste any time trying to find a DWM breechblock with a matching serial number... just get a replacement block and fit it to the gun and have fun shooting it.

If retaining matching numbers is important to you, then have the area of the original breechblock micro-welded and then remachined to the blueprint. But this will Not be cost effective in my opinion.