Here's what I've noticed on mine..
1. With the empty mag out, slide lock is easy to depress but slide will not lock open unless you manually press slide lock up while pulling back
2. With empty mag in, and slide pulled open, the mag follower makes it a bit hard to depress slide lock
3. Neither of the previous mentions allows slingshot operation
4. Mag fully loaded and in, sling shot operation works great

I've only shot a 100 rounds through mine so far and the issue I have is after the last round goes through, the slide doesn't always stay locked open? Someone told it still needs a bit longer to break in and then it shouldn't act up anymore. We shall see...