I own a Stoeger Cougar 8000 9 mm pistol and have had no problems at all after several thousand rounds and many IDPA matches. While at the range today, I experienced a problem I have never encountered. Following most double action shots and even a few single action shots, the slide lock engaged even though several rounds existed in the magazine. This occured with the Beretta magazines and aftermarket. I'm using the same ammo as I usually shoot which is 115 gr Winchester FMJ. After disassembly I dont see any issues with slide lock. The spring appears to be fine. The magazines appear to be fine as well. I dont see how this can happen with the magazine with rounds in it. Does anyone have any insight into this problem?

Thanks!