Question about deleting giveaways that have multiple copies

You can’t do re-roll if the issue is due to region locks, you can only request deletion.

...now just wait a second, you created a giveaway that was PROPERLY REGION LOCKED TO A SINGLE COUNTRY, yet one of the winners claims they cannot receive the gift (straight from Steam, even) due to region lock?
If that's the case, then you CAN ask for a reroll, as the issue was definitely NOT caused by you, you did your part:

FAQ -> Giveaways -> Creating -> What happens if I create a giveaway and the winner is unable to activate the gift in their region?
If you setup the giveaway with the appropriate region restrictions, and the winner was outside of those regions due to inaccurate information they provided, then you can request a new winner for the giveaway.

TL;DR: not your fault if somebody else faked their region, forgot to change it, or anything inbetween.
And now that creates another issue due to the time-limited nature of the sale, so going for a deletion might still be the best possible outcome for you.