Hello PerfectlyNormalBeast.

It is an issue with how Steam API reports ownership. It doesn't properly report bundles, collections or DLCs as owned and since the issue is from Steam's side, unfortunately there is nothing that Steamgifts can do to fix it. All we can do is encourage users to check for ownership before entering giveaways such as this.

Sure that would work, steamgifts can't delete the giveaway without your go ahead, which I think also involves opening another ticket, so your idea seems like the easiest fix