Cybergun FNX 45 decocking mechanism not working

[HappySpaceInvader]

In a nutshell, when I decock the hammer and then pull the trigger, a round is discharged (the slide goes back and sets the hammer back to single action position).

 

It's a Cybergun FNX-45 GBB Pistol that I just took delivery of a couple of days ago.  On the website where I bought it (Patrolbase) the decocking action is listed as one of the safety features.

 

On the FNX-45, you decock the hammer by pressing down on the safety, but on mine this only releases it to the halfway position - the same position the hammer goes back to during double action mode.

 

Is this a fault, or have I fundamentally misunderstood what decocking is supposed to acheive?  Please note, this is the first firearm of any kind I've owned that has such a feature.

 

Just wondering whether this is grounds for returning for replacement or refund from the site where I bought it.

Edited May 25 by HappySpaceInvader