I suspect your Kahr needs to go back to the factory.
I fired several early versions of the Kahr in the early 90’s and had the same problem, especially with +P+ ammo. These “nosedives” appeared to be caused by the slide velocity being a little too fast, which didn’t give the round in the magazine time to fully rise to the magazine feed lips before being pushed forward by the slide. (However, this won’t explain your misfeeds when manually loading it.)
Possibly your wife is having less of a problem because she’s holding the pistol less firmly, letting the whole pistol recoil in her hand a bit more than you do. This could be slowing the slide velocity down a little. Just out of curiosity, you might try holding the pistol less firm and see what happens. Obviously, this would not be a long-term solution to the problem.
The Kahr gives you a light weight but powerful pistol. The trade off is that it requires very strong springs, to include the magazine springs. I hate to admit it, but I wore my fingers raw loading the magazines and finally bought a SKS (I think) magazine loader.