I recently passed 500 rounds through my m&p 5.7 and this issue appeared. The first few hundred rounds I had no issues. Now within the last 200, sometimes the gun doesn't go all the way back into battery. The malfunction is easily fixed by lightly tapping the back of the slide. I'm cleaning/lubing it after every range trip. I haven't had any other issues with the pistol or the mags. Ammo has been Federal AE and Fiocchi Range Dynamics. Any advice besides sending it into S&W would be greatly appreciated.
EDIT: I have a holosun 507k mounted on it, in case the change in slide mass may be at fault here.