Maybe post a photo of the striker and spring and measure with a set of calipers. And also one of the light strikes.
I'll compare to a couple of my 99s. It might save having to pick up both.
I've been around quite a few 99s and have never seen a 99 with headspace issues before. The extractor should be holding the case enough to get a higher percentage of ignition. I'm leaning toward a weak spring as well.
You could start by swapping springs with the 44 and see if the light strike cartridges fire.
Just a thought, JT