Carefully "polish" the sharp edge of the slide latch where it contacts the magazine follower. Be careful not to round it too much.
These are stamped parts, and I've noticed that S&W generally hasn't done a very good job of cleaning up the edges of their stampings. That's part of the issue with the trigger as well.
Stamped cuts like this will often get worse during production over time as the dies wear, starting out fine with new dies, and finally getting to a point where the die has to be replaced or rebuilt. But if your part was made toward the end of the die's life, you may end up with burrs.
You'll probably have notches dug into the magazine followers now as well where the latch contacted them, and these would have to be smoothed out as well.
