Hi,
My WW1/2/3 frankenluger shooter, which has the DWM basics, a 1936 Mauser receiver and a VoPo barrel shows this pattern as well. Although a set of new springs did miracles for the gun, sometimes the extractor pops over the rim of a spent case.
It used to produce a small indent in the spent cartridges, but this has been cured by the new springs. They fly a bit higher as well
I believe my main problem is case length and although the 124 gr. Sellier & Bellot is just about the longest you can get, some are just a tad too short for this chamber/toggle combination.
There appears to be a distinct difference in size between the DWM toggle and the Mauser receiver and I have thought about swapping out one or the other (DWM receiver w. DWM toggle or Mauser receiver w. Mauser toggle).