Regrettably I can't tell you how to fix the slide lock issue although what your saying makes sense. To take the mags apart for cleaning, if they are like all the others I have seen, disassemble by pushing the round button or pin at the bottom of your base plate in with a phillips screw driver, etc. and slide the base plate pad off with your thumb. Be careful though because that button is the protruding part of the inner base plate connected directly to the spring assembly so it will be under tension. With thumb on that secondary plate release the tension and slide the whole inner assembly out comprising of that plate, spring and the follower. Bummer to hear about your mags and hope you can get it sorted out. Strange to happen with all 3 mags. Got some knowledgable folks here though that I'm sure can help you with that part of the equation.

Problem solved! Thanks, Tuefelhunden, here's how I did it. I took a Bic pen and pushed the round button at the bottom of the mag. While the pen is depressing the spring, press the 2 square panels on the bottom on both sides of the mag and bull the bottom of the mag off. I stretched the spring out a bit and put it back together. Problem solved. I found another problem, two of the springs are in great shape, one was coated in rust. I assume this is the one that I bought that did not come with the gun. Will HK replace this? I remember when I bought the mag, it was in new packaging.

You bet and glad you got 2 of the 3 sorted out. I have not had to use HK customer service so I don't know if they will or will not replace it for you but agree it is worth a try. If they don't the good thing is that springs should not cost that much. If not from HK directly Midway USA would be were I'd start my search to buy a replacement if HK doesn't hook you up on their dime. Good luck and thanks for the resolution tip. I have 3 HK's and if I encounter a mag problem I will try that. Makes sense as your putting more tension back onto that follower once reassembled.