Weapons bug?

[PZ]

Although I have no idea how it came about, I'm in Leboa, was at the beginning of the weapons dealer missions, and I already had the dart rifle in the armory.  Just to be sure I was remembering things correctly (I thought the dart came with the 4th arms dealer mission), I started doing the missions issued by the weapons dealer.

Sure enough, I did 3 of them and then the prompt came up that my next weapon would be the dart rifle - I've no idea how this came about.  I'm on the PC this evening - another thing, when playing on the console, after a weapons dealer mission is completed, a prompt displays asking if I want to save - this does not happen on the PC.

[Art Blade]

Our own guide says that it will be available when completing the fourth arms dealer mission.

[PZ]

Indeed - that's why it is so strange that I already had it at the beginning of the weapon dealer missions.  This is a PC saved game, so I wonder if something had corrupted at some time.  Unfortunately I'd started with this save from a long time ago, so I don't know it's history, other than I was at approximately 12% completion when I picked up this particular save.