The glory days of weapon duping in Dying Light appear to be over, as a small patch for the game says it addresses that particular problem. Whether a magical method of replicating weapons for free is really a “problem” during a zombie apocalypse is open to debate.
In game terms though, it was pretty clearly an unintentional bug.
Not a huge amount more in this patch, really. Specific Dying Light achievements are said to have been fixed (though it doesn’t say which ones,) and some incorrect “spit notifications” (lovely) in Be The Zombie mode have been sorted out as well.
Plus, there are some further, non-specific “performance improvements.”
Here’s the full changelog, because it’s actually short enough to post. If you haven’t yet received the patch, try restarting Steam.
Dying Light Patch 1.5.1.
• BTZ: Incorrect spit notifications fixed.
• Weapon duplication bug fixed.
• Specific achievements fixed.
• Various performance improvements.
• Windows/Linux cross play username and chat issues fixed.
• Quick travel to players in coop fixed.
• BTZ: UV block and Horde skills fixe.