I've previously owned 2 Kahr PM9 pistols.  Both shot great, never had reliability issues with one exception.  At the end of the day when I removed either gun from my pocket ( I used to have 4 different pocket holsters for them, I liked the gun that much ) the mag would Usually, not always, be released from the gun.  Just from sitting the mag would release.  I bought one of the guns used, so I bought another new and both had the same issue.  Never had a mag pop out shooting, or drawing, just from carrying in my pocket.  I've owned Rohrbaugh R9s, 1 diamondback, kel tec and ruger .380s and have simply never had this issue.  I called kahr and woman I spoke to (this is about 4 years ago) said she wasn't familiar with the problem.  Without getting into an argument about how poor their magazine release design is I should ask my question.  ARE THERE AFTERMARKET MAG RELEASES?  Are there any european style magazine lever/button modifications like the Rohrbaugh?  My Rohrbaugh was 100% reliable, I just couldn't hold onto it. MY PM9s shot great, I just couldn't trust them.

I suspect you're bumping the mag release against something.
Don't carry in a pocket without a holster that protects the mag release (as well as the trigger).

WOW, Did you read what I wrote?  The gun is at fault, not me.  We can play this game where you suppose, or guess, or think, or basically ignore what I said and blame me but that doesn't begin to answer my question.  The gun is too blame, the Kahr.  Is it a bad gun?  No.  It is however a poorly designed magazine release and i'd like to remedy that if i'm going to buy one.  I listed all the other guns i've pocket carried, and some IWB, and never had a single issue.....only the Kahr PM9 over and over. Strange.
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We heard you.

I've had a number of automatics that would release the magazine when carried without a magazine catch protecting holster when carried in the waistband, in a pocket, or in a fanny pack.
Among the guns were a S&W 3913, Colt Combat Commander, Walther PPK/s, Colt Officer's ACP, and my Kahr K9.

The K9 uses a coil type mag catch spring that's the same size as a 1911 catch spring so I replaced the K9 spring with a catch spring from a Colt Government Model.  That helped a bunch.
It would still do it once in a while and I finally cured it by installing a holster in the fanny pack that shrouded that mag catch.

The PM9 has a long, flat spring that powers the catch.
I seem to recall reading that other people have had issues with the polymer models having weak springs, and possibly issues with the mag catch itself.
Apparently Kahr now has a fix for the problem.
If not, most good pistolsmiths can probably fabricate and install a more powerful spring.

I'd give Kahr a call again and nicely ask about a fix.

The magazine release protrudes past the grip making it easy to accidentally release the mag.

I shortened the one on my CW9 to overcome the problem.

I removed the release and then filed it down to a height I felt worked best for me.
I also removed some plastic from the frame so it was still easy to press when wanted.
Then recut some serrations.

I don't know if you are up to doing something like this to your gun, but it worked for me.

Sorry for the crappy pic, but if you zoom in, you should be able to see what I did.

Thanks for the ideas guys.  It looks like you did a great job of bringing the release button down in size.

FWIW, My Kel-Tec P3AT mag would release when carried in my pocket. I carried it in a soft pocket holster (Desantis Nemesis). My PM9 never did that, even when carried in a similar pocket holster (Desantis SuperFly). The PM9, which I had  bought used, came with a plastic mag catch. I replaced it with a metal mag catch based on my experience with the P3AT. Something else to consider - maybe the mag catch spring is weak?