[bazacko]

Stop dry-firing without the mag in! The metal piece that pushes on the mag's valve receives a lot of stress this way. Mine broke and finding a replacement was a huge headache.

As for your problem - your hammer spring is definitely loose. In all likelihood, the bottom side of the spring (the one not pushed against the hammer) is not seated correctly. There is a "ledge" behind the hammer, on the left side (if the gun is pointing away from you). it's very narrow but this is where the other end of the spring needs to sit.

Hope this helps!

Edit: I just realized my advice about the dry-firing came too late!