I'm having problems after cleaning the slide won't go back all the way until I push that metal piece(don't know what it's called) on inside of gun to let it go all the way back. I tried changing slides with my other one and it works fine. It has done it both times when cleaning. It is a problem with the slide obviously, and it's not flush on that side like the other side. My problem is will S&W void the warranty because I put after market sights on it. It was shooting off so I changed sights now I think this is the problem.

Nobody to help a gal out with their knowledge about this.

Pic please if you can it will help.

Not sure from your description what metal piece you're referring to, but as for S&W warranty being void because you put aftermarket sights on it, my guess is that would void the warranty on about half (or more) of the M&Ps they have ever sold. Unless you damaged the slide during installation ofthe sights your warranty should be good on the rest of the gun, other than the non-original sights. Easiest way to find out is to call them. It's free!