It's the loaded chamber indicator on the top of the slide. It is touching the case of the bullet, and effects the way it ejects. I have the .40 cal 2.0 five inch barreled pistol, and have erratic ejections. My compact 2.0's don't have any trouble. Watch some you tube vids of the five inch 2.0 pistols...They all do it...I'm going to have mine milled off in the front so it doesn't toiuch the bullet casing - which also makes it no longer a loaded chamber indicator - which doesn't matter to me. I don't want or need that feature. I'm sure it will most likely void my warranty, and effect it's resale value, but I don't plan on selling it, and I'd just soon take my pistol to my gunsmith and pay if I encounter something I can't fix myself. My ejection isn't horrible, but I don't care, I want it to eject strong like every other .40 I've ever owned. It's the same in 9mm too. It's my only complaint on my five inch 2.0.