I've reloaded a fair amount of 9x19mm in my life, but never for a Luger. I've been told they're finicky. but I wonder if that's feed-ramp angle issue, or a feed-ramp roughness issue, or perhaps a ballistics issue.
If memory serves, Lugers are remarkably strong mechanisms and tend toward "stiffness", even when not new. The sheer geometry of the motions through which the articulating parts must go in a complete cycle kinda makes me wonder if a +P, or +P+ loading might improve feeding. Just a thought.