I am not a gunsmith nor have I ever been one, but I have owned, over the years, about 30 Lugers (My first collecting field when I was young with little money was Lugers), and I have shot most of them, in both calibers and in all barrel lengths except for the Luger Carbine, which I never owned.
Lugers are a very pretty pistol and full of history, but they are not a precision weapon. I can hear the screams now!!! Precision is when you can take apart 100 pistols and reassemble them at random, and 99 to 100 of them will still work perfectly. Lugers are a fine example of good German hand-fitting, but that is not precision manufacture as should apply to a military weapon. The hodge-podge of parts in your pistol is certainly an indication that malfunction can be expected. I have seen Lugers, all matching in numbers, in poor condition that still worked fairly well, but parts Lugers seldom do unless they have been treated to some real working over by a highly skilled gunsmith who fully understands the ins and outs of that particular pistol.
I would simply do your best to enjoy shooting the gun on the range, except the malfunctions you are getting, and NEVER stake your life on this gun, or in my opinion, and other Luger pistol, even mint and matching numbers.
They are grossly inferior as a weapon to pistols like the fine Belgian Browning GP Model, or the supreme Colt Government Model, or the more modern pistols like SIG-Sauer, Glock, Smith & Wesson, and the like.
I know this isn’t a gun foreum, so forgive me, but this relates directly to this gentleman’s ammunition questions.
By the way, it appears if at least some of that ammo is repacked. The emp label does not belong with any ammo I can see the markings on in your postings.