I have reported this bug quite a while ago, but since it didn’t get fixed with the inventory update I’ll post it here and perhaps our new Unlock Lead Organiser @Travis_IOI can take a look at this one pretty please.
To unlock the gold coin I reloaded a save several times to retry the challenge and ended up unlocking the coin more than once. Now I have a duplicate in my inventory which only shows up when online. In the offline version, this bug does not exist and I only have a single gold coin as normal.
What’s even stranger is that when selecting an agency pickup, the gold coin shows up four times. This only happens with small agency pickups, not with the large ones. I have not noticed any further exceptions to that rule; it seems to happen on all maps.