Shouldn't it be "Ustedes entregan"?
the noun la entrega is the delivery, but the way this sentence is worded , yes it should be entregan.
I don't know how to report the error then... It was listed as a correct answer. I got it wrong because I didn't choose it.
When you see an error like this, you can report it on the page right when it happens. The developers also monitor these forums, so they will probably see it here as well.