Okay so I think I figured out what's happening, based off what was said in that other forum post (adding the nut and all) and based on having to push up on the magazine.
So I had actually taken apart the pistol and looking and the knocker I noticed this
The knocker itself can float up a bit in it's channel. So my theory is that with the mag in, it can sometimes float to above the valve release which in its position in the first picture, it does that when I put the magazine with it
Either that or some kind of pistol gremlin is doing it. This would make sense with the nut thing if it means the valve release has a bigger area to be pressed. But then again I could just be completely off and dont know what I'm talking about